Oracle PL/SQL Programming

Calling Stored Procedures from PL/SQL Version 1.1Contents: Using Stubs to Talk to Server−Side PL/SQL Restrictions on Calling Stored Procedures The Oracle Developer/2000 tools use PL/SQL

Trang 2

Table of Contents

A What's on the Companion Disk? 2

A.1 Installing the Guide 2

3

A.2 Using the Guide 3

5

B Calling Stored Procedures from PL/SQL Version 1.1 6

B.1 Using Stubs to Talk to Server−Side PL/SQL 7

9

B.2 Restrictions on Calling Stored Procedures 9

B.2.1 No Server−Side PL/SQL Datatypes 9

B.2.2 No Direct Stored Package Variable References 10

B.2.3 No Direct Remote Procedure Calls 12

B.2.4 No Default Parameter Values 12

14

C Built−In Packages 15

C.1 Using the Built−in Packages 16

18

C.2 DBMS_ALERT 18

C.2.1 The REGISTER procedure 18

C.2.2 The REMOVE procedure 18

C.2.3 The REMOVEALL procedure 18

C.2.4 The SET_DEFAULTS procedure 18

C.2.5 The SIGNAL procedure 18

C.2.6 The WAITANY procedure 19

C.2.7 The WAITONE procedure 19

20

C.3 Oracle AQ, the Advanced Queueing Facility 20

C.3.1 DBMS_AQ (PL/SQL 8 Only) 20

C.3.2 DBMS_AQADM (PL/SQL 8 Only) 21

24

C.4 DBMS_DDL 24

C.4.1 The ALTER_COMPILE procedure 24

C.4.2 The ANALYZE_OBJECT procedure 24

25

C.5 DBMS_ JOB 25

C.5.1 The BROKEN procedure 25

C.5.2 The CHANGE procedure 25

C.5.3 The INTERVAL procedure 25

C.5.4 The ISUBMIT procedure 25

C.5.5 The NEXT_DATE procedure 26

C.5.6 The REMOVE procedure 26

C.5.7 The RUN procedure 26

C.5.8 The SUBMIT procedure 26

C.5.9 The USER_EXPORT procedure 26

C.5.10 The WHAT procedure 26

28

C.6 DBMS_LOB (PL/SQL8 Only) 28

C.6.1 The APPEND procedure 28

C.6.2 The COMPARE function 28

C.6.3 The COPY procedure 29

[Appendix A] What's on the Companion Disk?

i

Trang 3

C.6.4 The ERASE procedure 29

C.6.5 The FILECLOSE procedure 29

C.6.6 The FILECLOSEALL procedure 29

C.6.7 The FILEEXISTS function 29

C.6.8 The FILEGETNAME procedure 29

C.6.9 The FILEISOPEN function 30

C.6.10 The FILEOPEN procedure 30

C.6.11 The GETLENGTH function 30

C.6.12 The INSTR function 30

C.6.13 The READ procedure 30

C.6.14 The SUBSTR function 31

C.6.15 The TRIM procedure 31

C.6.16 The WRITE procedure 31

33

C.7 DBMS_LOCK 33

C.7.1 The ALLOCATE_UNIQUE procedure 33

C.7.2 The CONVERT function 33

C.7.3 The RELEASE function 34

C.7.4 The REQUEST function 34

C.7.5 The SLEEP procedure 34

36

C.8 DBMS_MAIL 36

C.8.1 The SEND procedure 36

37

C.9 DBMS_OUTPUT 37

C.9.1 The DISABLE procedure 37

C.9.2 The ENABLE procedure 37

C.9.3 The GET_LINE procedure 37

C.9.4 The GET_LINES procedure 37

C.9.5 The NEW_LINE procedure 37

C.9.6 The PUT procedure 38

C.9.7 The PUT_LINE procedure 38

39

C.10 DBMS_PIPE 39

C.10.1 The CREATE_PIPE function 39

C.10.2 The NEXT_ITEM_TYPE function 39

C.10.3 The PACK_MESSAGE procedure 40

C.10.4 The PURGE procedure 40

C.10.5 The RECEIVE_MESSAGE function 40

C.10.6 The REMOVE_PIPE function 40

C.10.7 The RESET_BUFFER procedure 40

C.10.8 The SEND_MESSAGE function 41

C.10.9 The UNIQUE_SESSION_NAME function 41

C.10.10 The UNPACK_MESSAGE procedure 41

42

C.11 DBMS_ROWID (PL/SQL8 Only) 42

C.11.1 The ROWID_CREATE function 42

C.11.2 The ROWID_INFO procedure 42

C.11.3 The ROWID_TYPE function 42

C.11.4 The ROWID_OBJECT function 42

C.11.5 The ROWID_RELATIVE_FNO function 43

C.11.6 The ROWID_BLOCK_NUMBER function 43

ii

Trang 4

C.11.7 The ROWID_ROW_NUMBER function 43

C.11.8 The ROWID_TO_ABSOLUTE_FNO function 43

C.11.9 The ROWID_TO_EXTENDED function 43

C.11.10 The ROWID_TO_RESTRICTED function 43

C.11.11 The ROWID_VERIFY function 43

45

C.12 DBMS_SESSION 45

C.12.1 The CLOSE_DATABASE_LINK procedure 45

C.12.2 The IS_ROLE_ENABLED function 45

C.12.3 The RESET_PACKAGE procedure 45

C.12.4 The SET_LABEL procedure 45

C.12.5 The SET_NLS_LABEL procedure 45

C.12.6 The SET_NLS procedure 45

C.12.7 The SET_ROLE procedure 46

C.12.8 The SET_SQL_TRACE procedure 46

C.12.9 The UNIQUE_SESSION_ID function 46

47

C.13 DBMS_SNAPSHOT 47

C.13.1 The DROP_SNAPSHOT procedure 47

C.13.2 The GET_LOG_AGE procedure 47

C.13.3 The PURGE_LOG procedure 47

C.13.4 The REFRESH procedure 47

C.13.5 The REFRESH_ALL procedure 48

C.13.6 The SET_UP procedure 48

C.13.7 The WRAP_UP procedure 48

49

C.14 DBMS_SQL 49

C.14.1 The BIND_ARRAY procedure 49

C.14.2 The BIND_VARIABLE procedure 49

C.14.3 The CLOSE_CURSOR procedure 50

C.14.4 The COLUMN_VALUE procedure 50

C.14.5 The DEFINE_COLUMN procedure 51

C.14.6 The EXECUTE function 51

C.14.7 The EXECUTE_AND_FETCH function 52

C.14.8 The FETCH_ROWS function 52

C.14.9 The IS_OPEN function 52

C.14.10 The LAST_ERROR_POSITION function 52

C.14.11 The LAST_ROW_COUNT function 52

C.14.12 The LAST_ROW_ID function 52

C.14.13 The LAST_SQL_FUNCTION_CODE function 52

C.14.14 The OPEN_CURSOR function 53

C.14.15 The PARSE procedure 53

C.14.16 The VARIABLE_VALUE procedure 53

54

C.15 DBMS_TRANSACTION 54

C.15.1 The ADVISE_COMMIT procedure 54

C.15.2 The ADVISE_NOTHING procedure 54

C.15.3 The ADVISE_ROLLBACK procedure 54

C.15.4 The COMMIT procedure 55

C.15.5 The COMMIT_COMMENT procedure 55

C.15.6 The COMMIT_FORCE procedure 55

C.15.7 The READ_ONLY procedure 55

iii

Trang 5

C.15.8 The READ_WRITE procedure 55

C.15.9 The ROLLBACK procedure 56

C.15.10 The ROLLBACK_FORCE procedure 56

C.15.11 The ROLLBACK_SAVEPOINT procedure 56

C.15.12 The SAVEPOINT procedure 56

C.15.13 The USE_ROLLBACK_SEGMENT procedure 56

C.15.14 The BEGIN_DISCRETE_TRANSACTION procedure 56

C.15.15 The PURGE_MIXED procedure 57

C.15.16 The PURGE_LOST_DB procedure 57

C.15.17 The LOCAL_TRANSACTION_ID function 57

C.15.18 The STEP_ID function 57

59

C.16 DBMS_UTILITY 59

C.16.1 The ANALYZE_SCHEMA procedure 59

C.16.2 The COMMA_TO_TABLE procedure 59

C.16.3 The COMPILE_SCHEMA procedure 59

C.16.4 The FORMAT_CALL_STACK function 59

C.16.5 The FORMAT_ERROR_STACK function 59

C.16.6 The GET_TIME function 60

C.16.7 The IS_PARALLEL_SERVER function 60

C.16.8 The NAME_RESOLVE procedure 60

C.16.9 The NAME_TOKENIZE procedure 60

C.16.10 The PORT_STRING function 61

C.16.11 The TABLE_TO_COMMA procedure 61

62

C.17 UTL_FILE 62

C.17.1 Setting Up UTL_FILE 62

65

1 Introduction to PL/SQL 66

1.1 What Is PL/SQL? 66

68

1.2 The Concept of Programming in Oracle Applications 68

70

1.3 The Origins of PL/SQL 70

1.3.1 Improved Application Portability with PL/SQL 70

1.3.2 Improved Execution Authority and Transaction Integrity with PL/SQL 71

72

1.4 PL/SQL Versions 72

1.4.1 Working with Multiple Versions of PL/SQL 72

1.4.2 How This Book Handles Different Versions of PL/SQL 73

1.4.3 PL/SQL Version 2.0 73

1.4.4 PL/SQL Release 2.1 80

1.4.7 PL/SQL Version 8.0 84

88

1.5 Advice for Oracle Programmers 88

1.5.1 Take a Creative, Even Radical Approach 88

1.5.2 Get Ready to Establish New Habits 88

1.5.3 Assume that PL/SQL Has What You Need 89

iv

Trang 6

1.5.4 Share Your Ideas 90

91

1.6 A Few of My Favorite (PL/SQL) Things 91

1.6.1 Anchored declarations 91

1.6.2 Built−in functions 91

1.6.3 Built−in packages 91

1.6.4 The cursor FOR loop 92

1.6.5 Scoping with nested blocks 92

1.6.6 Module overloading 92

1.6.7 Local modules 93

1.6.8 Packages 93

95

1.7 Best Practices for PL/SQL Excellence 95

1.7.1 Write as Little Code as Possible 95

1.7.2 Synchronize Program and Data Structures 96

1.7.3 Center All Development Around Packages 97

1.7.4 Standardize Your PL/SQL Development Environment 98

1.7.5 Structured Code and Other Best Practices 98

101

2 PL/SQL Language Fundamentals 102

2.1 The PL/SQL Character Set 102

104

2.2 Identifiers 104

2.2.1 Reserved Words 105

2.2.2 Whitespace and Keywords 106

107

2.3 Literals 107

2.3.1 Embedding Single Quotes Inside a String 107

2.3.2 Numeric Literals 108

2.3.3 Boolean Literals 108

110

2.4 The Semicolon Delimiter 110

111

2.5 Comments 111

2.5.1 Single−Line Comment Syntax 111

2.5.2 Multiline Comment Syntax 111

113

2.6 The PRAGMA Keyword 113

114

2.7 Block Structure 114

2.7.1 Sections of the PL/SQL Block 114

2.7.2 Scope of a Block 115

2.7.3 Nested Blocks 115

117

3 Effective Coding Style 118

3.1 Fundamentals of Effective Layout 118

3.1.1 Revealing Logical Structure with Indentation 119

3.1.2 Using Case to Aid Readability 120

3.1.3 The UPPER−lower Style 120

3.1.4 Formatting Single Statements 121

v

Trang 7

3 Effective Coding Style

3.1.5 Formatting Your Declarations 122

3.1.6 Formatting Multiline Statements 123

126

3.2 Formatting SQL Statements 126

129

3.3 Formatting Control Structures 129

3.3.1 Formatting IF Statements 129

3.3.2 Formatting Loops 130

3.3.3 Formatting Exception Handlers 131

133

3.4 Formatting PL/SQL Blocks 133

135

3.5 Formatting Packages 135

137

3.6 Using Comments Effectively 137

3.6.1 Comment As You Code 138

3.6.2 Explain the Why −− Not the How −− of Your Program 138

3.6.3 Make Comments Easy to Enter and Maintain 139

3.6.4 Maintain Indentation 140

3.6.5 Comment Declaration Statements 141

143

3.7 Documenting the Entire Package 143

3.7.1 Document the Package Specification 143

3.7.2 Document the Package Body 144

146

4 Variables and Program Data 147

4.1 Identifiers 147

4.1.1 Choose the Right Name 147

4.1.2 Select Readable Names 148

149

4.2 Scalar Datatypes 149

4.2.1 Numeric Datatypes 150

4.2.2 Numeric Subtypes 152

4.2.3 Character Datatypes 153

4.2.4 The Boolean Datatype 160

4.2.5 The Date−Time Datatype 160

4.2.6 NLS Character Datatypes 161

4.2.7 LOB Datatypes 162

4.2.8 Conversion Between Datatypes 166

169

4.3 NULLs in PL/SQL 169

4.3.1 NULL Values in Comparisons 170

4.3.2 Checking for NULL Values 170

4.3.3 Function Results with NULL Arguments 171

173

4.4 Variable Declarations 173

4.4.1 Constrained Declarations 173

4.4.2 Declaration Examples 173

4.4.3 Default Values 174

4.4.4 NOT NULL Clause 175

vi

Trang 8

4.5.1 Benefits of Anchored Declarations 176

4.5.2 Anchoring at Compile Time 176

4.5.3 Nesting Usages of the %TYPE Attribute 177

4.5.4 Anchoring to Variables in Other PL/SQL Blocks 178

4.5.5 Anchoring to NOT NULL Datatypes 179

179

4.5 Anchored Declarations 179

181

4.6 Programmer−Defined Subtypes 181

4.6.1 Declaring Subtypes 181

4.6.2 Examples of Subtype Declarations 182

4.6.3 Emulating Constrained Subtypes 183

185

4.7 Tips for Creating and Using Variables 185

4.7.1 Establish Clear Variable Naming Conventions 185

4.7.2 Name Subtypes to Self−Document Code 187

4.7.3 Avoid Recycling Variables 188

4.7.4 Use Named Constants to Avoid Hardcoding Values 188

4.7.5 Convert Variables into Named Constants 189

4.7.6 Remove Unused Variables from Programs 190

4.7.7 Use %TYPE When a Variable Represents a Column 190

4.7.8 Use %TYPE to Standardize Nondatabase Declarations 191

4.7.9 Use Variables to Hide Complex Logic 192

196

5 Conditional and Sequential Control 197

5.1 Conditional Control Statements 197

5.1.1 The IF−THEN Combination 197

5.1.2 The IF−THEN−ELSE Combination 198

5.1.3 The IF−ELSIF Combination 199

5.1.4 Nested IF Statements 203

205

5.2 Sequential Control Statements 205

5.2.1 The GOTO Statement 205

5.2.2 The NULL Statement 208

211

6 Database Interaction and Cursors 212

6.1 Transaction Management 212

6.1.1 The COMMIT Statement 213

6.1.2 The ROLLBACK Statement 213

6.1.3 The SAVEPOINT Statement 214

6.1.4 The SET TRANSACTION Statement 214

6.1.5 The LOCK TABLE Statement 215

217

6.2 Cursors in PL/SQL 217

6.2.1 Types of Cursors 218

6.2.2 Cursor Operations 218

220

6.3 Implicit and Explicit Cursors 220

6.3.1 Implicit Cursors 220

6.3.2 Drawbacks of Implicit Cursors 220

vii

Trang 9

6.3.3 Explicit Cursors 222

224

6.4 Declaring Cursors 224

6.4.1 The Cursor Name 224

6.4.2 PL/SQL Variables in a Cursor 225

6.4.3 Identifier Precedence in a Cursor 225

6.4.4 The Cursor RETURN Clause 226

229

6.5 Opening Cursors 229

231

6.6 Fetching from Cursors 231

6.6.1 Matching Column List with INTO Clause 231

6.6.2 Fetching Past the Last Row 233

234

6.7 Column Aliases in Cursors 234

236

6.8 Closing Cursors 236

6.8.1 Maximum Number of Cursors 236

6.8.2 Closing Local Cursors 237

238

6.9 Cursor Attributes 238

6.9.1 The %FOUND Attribute 239

6.9.2 The %NOTFOUND Attribute 240

6.9.3 The %ROWCOUNT Attribute 240

6.9.4 The %ISOPEN Attribute 241

6.9.5 Implicit SQL Cursor Attributes 241

6.9.6 Differences Between Implicit and Explicit Cursor Attributes 241

243

6.10 Cursor Parameters 243

6.10.1 Generalizing Cursors with Parameters 244

6.10.2 Opening Cursors with Parameters 244

6.10.3 Scope of Cursor Parameters 245

6.10.4 Cursor Parameter Modes 245

6.10.5 Default Values for Parameters 245

246

6.11 SELECT FOR UPDATE in Cursors 246

6.11.1 Releasing Locks with COMMIT 247

6.11.2 The WHERE CURRENT OF Clause 248

6.12.1 Features of Cursor Variables 250

6.12.2 Similarities to Static Cursors 250

6.12.3 Declaring REF CURSOR Types and Cursor Variables 251

6.12.4 Opening Cursor Variables 252

6.12.5 Fetching from Cursor Variables 253

6.12.6 Rules for Cursor Variables 254

6.12.7 Passing Cursor Variables as Arguments 255

6.12.8 Cursor Variable Restrictions 257

260

6.12 Cursor Variables 262

264

6.13 Working with Cursors 264

6.13.1 Validating Foreign Key Entry with Cursors 264

6.13.2 Managing a Work Queue with SELECT FOR UPDATE 266

270viii

Trang 10

7 Loops 271

7.1 Loop Basics 271

7.1.1 Examples of Different Loops 271

7.1.2 Structure of PL/SQL Loops 272

274

7.2 The Simple Loop 274

7.2.1 Terminating a Simple Loop: EXIT and EXIT WHEN 275

7.2.2 Emulating a REPEAT UNTIL Loop 276

277

7.3 The Numeric FOR Loop 277

7.3.1 Rules for Numeric FOR Loops 277

7.3.2 Examples of Numeric FOR Loops 278

7.3.3 Handling Nontrivial Increments 279

280

7.4 The Cursor FOR Loop 280

7.4.1 Example of Cursor FOR Loops 280

7.4.2 The Cursor FOR Loop Record 281

7.4.3 When to Use the Cursor FOR Loop 282

284

7.5 The WHILE Loop 284

7.5.1 The Infinite WHILE Loop 285

286

7.6 Managing Loop Execution 286

7.6.1 Loop Labels 286

7.6.2 Loop Scope 288

290

7.7 Tips for PL/SQL Loops 290

7.7.1 Naming Loop Indexes 290

7.7.2 The Proper Way to Say Goodbye 291

7.7.3 Avoiding the Phony Loop 293

7.7.4 PL/SQL Loops Versus SQL Processing 293

8.1 Why Exception Handling? 296

297

8 Exception Handlers 298

300

8.2 The Exception Section 300

302

8.3 Types of Exceptions 302

8.3.1 Named System Exceptions 302

8.3.2 Named Programmer−Defined Exceptions 304

8.3.3 Unnamed System Exceptions 305

8.3.4 Unnamed Programmer−Defined Exceptions 306

308

8.4 Determining Exception−Handling Behavior 308

8.4.1 Scope of an Exception 308

8.4.2 Propagation of an Exception 312

315

8.5 Raising an Exception 315

8.5.1 Who Raises the Exception? 315

8.5.2 Re−Raising an Exception 316

8.5.3 Exceptions Raised in a Declaration 317

ix

Trang 11

8.5.4 Exceptions Raised in an Exception Handler 317

320

8.6 Handling Exceptions 320

8.6.1 Combining Multiple Exceptions in a Single Handler 320

8.6.2 Unhandled Exceptions 321

8.6.3 Using SQLCODE and SQLERRM in WHEN OTHERS Clause 321

8.6.4 Continuing Past Exceptions 322

325

8.7 Client−Server Error Communication 325

8.7.1 Using RAISE_APPLICATION_ERROR 325

8.7.2 RAISE_APPLICATION_ERROR in a database trigger 325

327

8.8 NO_DATA_FOUND: Multipurpose Exception 327

329

8.9 Exception Handler as IF Statement 329

331

8.10 RAISE Nothing but Exceptions 331

334

9 Records in PL/SQL 335

9.1 Record Basics 335

9.1.1 Different Types of Records 335

9.1.2 Accessing Record−Based Data 336

9.1.3 Benefits of Using Records 336

9.1.4 Guidelines for Using Records 337

9.1.5 Referencing a Record and its Fields 338

9.1.6 Comparing Two Records 338

340

9.2 Table−Based Records 340

9.2.1 Declaring Records with the %ROWTYPE Attribute 340

342

9.3 Cursor−Based Records 342

9.3.1 Choosing Columns for a Cursor Record 342

9.3.2 Setting the Record's Column Names 343

345

9.4 Programmer−Defined Records 345

9.4.1 Declaring Programmer−Defined Record TYPEs 345

9.4.2 Declaring the Record 346

9.4.3 Examples of Programmer−Defined Record Declarations 347

349

9.5 Assigning Values to and from Records 349

9.5.1 Direct Field Assignment 349

9.5.2 SELECT INTO from an Implicit Cursor 350

9.5.3 FETCH INTO from an Explicit Cursor 350

9.5.4 Aggregate Assignment 351

352

9.6 Record Types and Record Compatibility 352

9.6.1 Assignment Restrictions 353

9.6.2 Record Initialization 353

355x

Trang 12

9.7 Nested Records 355

9.7.1 Example of Nested Records 355

9.7.2 Dot Notation with Nested Records 356

9.7.3 Aggregate Assignments of Nested Records 356

9.7.4 Denormalizing Program Data with Nested Records 357

10.1 PL/SQL Tables and Other Collections 360

10.1.1 PL/SQL Tables 361

10.1.2 Nested Tables and VARRAYs 362

362

10 PL/SQL Tables 362

363

10.2 Characteristics of PL/SQL Tables 363

365

10.3 PL/SQL Tables and DML Statements 365

366

10.4 Declaring a PL/SQL Table 366

10.4.1 Defining the Table TYPE 366

10.4.2 Declaring the PL/SQL Table 367

368

10.5 Referencing and Modifying PL/SQL Table Rows 368

10.5.1 Automatic Conversion of Row Number Expressions 368

10.5.2 Referencing an Undefined Row 368

10.5.3 Nonsequential Use of PL/SQL Table 369

10.5.4 Passing PL/SQL Tables as Parameters 370

372

10.6 Filling the Rows of a PL/SQL Table 372

10.6.1 Direct Assignment 372

10.6.2 Iterative Assignment 372

10.6.3 Aggregate Assignment 373

374

10.7 Clearing the PL/SQL Table 374

376

10.8 PL/SQL Table Enhancements in PL/SQL Release 2.3 376

10.8.1 PL/SQL Tables of Records 377

10.8.2 PL/SQL Table Built−ins 379

383

10.9 Working with PL/SQL Tables 383

10.9.1 Transferring Database Information to PL/SQL Tables 383

10.9.2 Data−Smart Row Numbers in PL/SQL Tables 384

10.9.3 Displaying a PL/SQL Table 386

10.9.4 Building Traditional Arrays with PL/SQL Tables 391

10.9.5 Optimizing Foreign Key Lookups with PL/SQL Tables 397

404

11 Character Functions 405

11.1 Character Function Descriptions 406

11.1.1 The ASCII function 406

11.1.2 The CHR function 406

11.1.3 The CONCAT function 407

11.1.4 The INITCAP function 408

11.1.5 The INSTR function 409

xi

Trang 13

11 Character Functions

11.1.6 The LENGTH function 412

11.1.7 The LOWER function 412

11.1.8 The LPAD function 413

11.1.9 The LTRIM function 414

11.1.10 The REPLACE function 415

11.1.11 The RPAD function 418

11.1.12 The RTRIM function 419

11.1.13 The SOUNDEX function 420

11.1.14 The SUBSTR function 420

11.1.15 The TRANSLATE function 424

11.1.16 The UPPER function 425

426

11.2 Character Function Examples 426

11.2.1 Parsing a Name 426

11.2.2 Implementing Word Wrap for Long Text 431

11.2.3 Filling Text to Fit a Line 434

11.2.4 Counting Substring Occurrences in Strings 436

11.2.5 Verifying String Formats with TRANSLATE 438

441

12 Date Functions 442

12.1 Date Function Descriptions 443

12.1.1 The ADD_MONTHS function 443

12.1.2 The LAST_DAY function 444

12.1.3 The MONTHS_BETWEEN function 445

12.1.4 The NEW_TIME function 446

12.1.5 The NEXT_DAY function 447

12.1.6 The ROUND function 448

12.1.7 The SYSDATE function 450

12.1.8 The TRUNC function 450

453

12.2 Date Function Examples 453

12.2.1 Customizing the Behavior of ADD_MONTHS 453

12.2.2 Using NEW_TIME in Client−Server Environments 454

459

13 Numeric, LOB, and Miscellaneous Functions 460

13.1 Numeric Function Descriptions 461

13.1.1 The ABS function 461

13.1.2 The ACOS function 462

13.1.3 The ASIN function 462

13.1.4 The ATAN function 462

13.1.5 The ATAN2 function 462

13.1.6 The CEIL function 463

13.1.7 The COS function 464

13.1.8 The COSH function 464

13.1.9 The EXP function 464

13.1.10 The FLOOR function 464

13.1.11 The LN function 465

13.1.12 The LOG function 465

13.1.13 The MOD function 465

xii

Trang 14

13 Numeric, LOB, and Miscellaneous Functions

13.1.14 The POWER function 465

13.1.15 The ROUND function 466

13.1.16 The SIGN function 466

13.1.17 The SIN function 466

13.1.18 The SINH function 467

13.1.19 The SQRT function 467

13.1.20 The TAN function 467

13.1.21 The TANH function 467

13.1.22 The TRUNC function 467

13.1.23 Rounding and Truncation with PL/SQL 468

469

13.2 LOB Function Descriptions 469

13.2.1 The BFILENAME function 469

13.2.2 The EMPTY_BLOB function 471

13.2.3 The EMPTY_CLOB function 471

472

13.3 Miscellaneous Function Descriptions 472

13.3.1 The DUMP function 472

13.3.2 The GREATEST function 473

13.3.3 The LEAST function 473

13.3.4 The NVL function 473

13.3.5 The SQLCODE function 475

13.3.6 The SQLERRM function 475

13.3.7 The UID function 476

13.3.8 The USER function 476

13.3.9 The USERENV function 477

13.3.10 The VSIZE function 478

479

14 Conversion Functions 480

14.1 Conversion Formats 480

14.1.1 Date Format Models 481

14.1.2 Number Format Models 483

486

14.2 Conversion Function Descriptions 486

14.2.1 The CHARTOROWID function 486

14.2.2 The CONVERT function 486

14.2.3 The HEXTORAW function 486

14.2.4 The RAWTOHEX function 487

14.2.5 The ROWIDTOCHAR function 487

14.2.6 The TO_CHAR function (date conversion) 487

14.2.7 The TO_CHAR function (number conversion) 488

14.2.8 The TO_DATE function 488

14.2.9 The TO_NUMBER function 490

491

14.3 Conversion Function Examples 491

14.3.1 FM: Suppressing Blanks and Zeros 491

14.3.2 FX: Matching Formats Exactly 492

14.3.3 RR: Changing Millenia 493

14.3.4 Using TO_CHAR to Create a Date Range 494

14.3.5 Building a Date Manager 498

xiii

Trang 15

15.2.1 Sequence of Section Construction 508

15.2.2 PL/SQL Block Structure Examples 509

15.3.1 The Structure of an Anonymous Block 509

15.3.2 Examples of Anonymous Blocks 512

15.3.3 Anonymous Blocks in the Oracle Tools 512

15.3.4 Nested Blocks 513

15.3.5 Scope and Visibility 513

15.3.6 Block Labels 515

15.4.1 Calling a Procedure 515

15.4.2 Procedure Header 515

15.4.3 Procedure Body 516

15.4.4 The END Label 516

517

15 Procedures and Functions 521

15.1 Modular Code 525

527

15.2 Review of PL/SQL Block Structure 527

528

15.3 The Anonymous PL/SQL Block 528

529

15.4 Procedures 529

530

15.5 Functions 530

15.5.1 Structure of a Function 530

15.5.2 The RETURN Datatype 531

15.5.3 The END Label 532

15.5.4 Calling a Function 532

15.5.5 Function Header 533

15.5.6 Function Body 534

15.5.7 A Tiny Function 534

15.5.8 The RETURN Statement 534

537

15.6 Parameters 537

15.6.1 Defining the Parameters 537

15.6.2 Parameter Modes 538

15.6.3 Actual and Formal Parameters 541

15.6.4 Matching Actual and Formal Parameters in PL/SQL 542

15.6.5 Default Values 544

545

15.7 Local Modules 545

15.7.1 Benefits of Local Modularization 545

15.7.2 Reducing Code Volume 546

15.7.3 Improving Readability 546

15.7.4 BottomưUp Reading 548

15.7.5 Scope of Local Modules 548

15.7.6 Spruce Up Your Code with Local Modules! 548

549

15.8 Module Overloading 549

15.8.1 Overloading in PL/SQL BuiltưIns 549

15.8.2 Benefits of Overloading 550

15.8.3 Where to Overload Modules 550

xiv

Trang 16

15.8.4 Restrictions on Overloading 551

554

15.9 Forward Declarations 554

556

15.10 Go Forth and Modularize! 556

557

16 Packages 558

16.1 The Benefits of Packages 559

16.1.1 Enforced Information Hiding 559

16.1.2 Object−Oriented Design 559

16.1.3 Top−Down Design 559

16.1.4 Object Persistence 559

16.1.5 Performance Improvement 560

561

16.2 Overview of Package Structure 561

16.2.1 The Specification 561

16.2.2 The Body 562

16.2.3 Package Syntax 562

16.2.4 Public and Private Package Elements 563

16.2.5 How to Reference Package Elements 564

16.2.6 Quick Tour of a Package 565

569

16.3 The Package Specification 569

16.3.1 Packages Without Bodies 570

16.3.2 Declaring Package Cursors 573

575

16.4 The Package Body 575

16.4.1 Declare in Specification or Body 575

16.4.2 Synchronize Body with Package 576

578

16.5 Package Data 578

16.5.1 Architecture of Package−Based Data 578

16.5.2 Global Within a Single Oracle Session 579

16.5.3 Global Public Data 579

16.5.4 Global Private Data 580

16.5.5 Providing an Interface to Global Data 581

583

16.6 Package Initialization 583

16.6.1 Drawbacks of Package Initialization 583

16.6.2 Use Initialization Section for Complex Logic 583

16.6.3 Side Effects 584

16.6.4 Load Session Data in Initialization Section 584

586

17 Calling PL/SQL Functions in SQL 587

17.1 Looking at the Problem 587

590

17.2 Syntax for Calling Stored Functions in SQL 590

592

xv

Trang 17

17.3 Requirements for Stored Functions in SQL 592

594

17.4 Restrictions on PL/SQL Functions in SQL 594

596

17.5 Calling Packaged Functions in SQL 596

17.5.1 The RESTRICT_REFERENCES Pragma 596

17.5.2 Asserting Purity Level with Package Initialization Section 598

600

17.6 Column/Function Name Precedence 600

601

17.7 Realities: Calling PL/SQL Functions in SQL 601

17.7.1 Manual Application of Pragmas 601

17.7.2 Read Consistency Model Complications 602

604

17.8 Examples of Embedded PL/SQL 604

17.8.1 Encapsulating Calculations 604

17.8.2 Combining Scalar and Aggregate Values 605

17.8.3 Replacing Correlated Subqueries 607

17.8.4 Replacing DECODEs with IF Statements 609

17.8.5 GROUP BY Partial Column Values 611

17.8.6 Sequential Processing Against a Column's Value 612

17.8.7 Recursive Processing in a SQL Statement 613

616

18 Object Types 617

18.1 Introduction to Oracle8 Objects 618

18.1.1 Terminology 618

18.1.2 Some Simple Examples 619

18.1.3 Comparison: Oracle8 Objects and Earlier Features 620

18.1.4 Characteristics of Objects 621

18.1.5 Object Programming Themes 623

627

18.2 Oracle Objects Example 627

18.2.1 Defining the Object Type Specification 627

18.2.2 Defining the Object Type Body 627

18.2.3 Adding Complex Data Structures 631

634

18.3 Syntax for Creating Object Types 634

18.3.1 About Object Types 634

18.3.2 CREATE TYPE and DROP TYPE: Creating and Dropping Types 634

18.3.3 CREATE TYPE BODY: Creating a Body 636

18.3.4 Dot Notation 636

18.3.5 SELF: The Implied Parameter 639

18.3.6 Comparing Objects 640

18.3.7 Privileges 643

645

18.4 Manipulating Objects in PL/SQL and SQL 645

18.4.1 The Need to Initialize 645

18.4.2 OID, VALUE, REF, and DEREF 647

655xvi

Trang 18

18.5 Modifying Persistent Objects 655

18.5.1 Approach 1: Permit Full Use of Conventional SQL 656

18.5.2 Approach 2: Define Methods and Permit Limited Use of Conventional SQL 657

18.5.3 Approach 3: Do Everything via Methods 658

18.5.4 Approach 4: Use an Object and a PL/SQL Container Package 664

18.5.5 Implications for Developer/2000 667

668

18.6 Object Housekeeping 668

18.6.1 Data Dictionary 668

18.6.2 SQL*Plus "Describe" Command 669

18.6.3 Schema Evolution 669

672

18.7 Making the Objects Option Work 672

674

19 Nested Tables and VARRAYs 675

19.1 Types of Collections 675

680

19.2 Creating the New Collections 680

19.2.1 Collections "In the Database" 680

19.2.2 Collections in PL/SQL 682

687

19.3 Syntax for Declaring Collection Datatypes 687

689

19.4 Using Collections 689

19.4.1 Initializing Collection Variables 689

19.4.2 Assigning Values to Elements: Index (Subscript) Considerations 693

19.4.3 Adding and Removing Elements 693

19.4.4 Comparing Collections 695

697

19.5 Collection Pseudo−Functions 697

19.5.1 The THE Pseudo−function 697

19.5.2 The CAST Pseudo−function 699

19.5.3 The MULTISET Pseudo−function 700

19.5.4 The TABLE Pseudo−function 702

704

19.6 Collection Built−Ins 704

19.6.1 COUNT 705

19.6.2 DELETE [ ( i [ , j ] ) ] 705

19.6.3 EXISTS(i) 706

19.6.4 EXTEND [ (n [,i] ) ] 706

19.6.5 FIRST, LAST 707

19.6.6 LIMIT 707

19.6.7 PRIOR(i), NEXT(i) 708

19.6.8 TRIM [ (n ) ] 708

710

19.7 Example: PL/SQL−to−Server Integration 710

713

19.8 Collections Housekeeping 713

19.8.3 Call by Reference or Call by Value 714

715

xvii

Trang 19

19.9 Which Collection Type Should I Use? 715

20.1 Example: Using Object Views 716

717

20 Object Views 718

723

20.2 INSTEAD OF Triggers 723

20.2.1 INSTEAD OF Triggers: To Use or Not to Use? 724

727

20.3 Syntax for Object Views 727

20.3.1 CREATE VIEW: Creating an Object View 727

20.3.2 DROP: Dropping Views and Triggers 728

20.3.3 MAKE_REF: Returning a Virtual REF 728

730

20.4 Differences Between Object Views and Object Tables 730

20.4.1 OID Uniqueness 730

20.4.2 Using REFs with Object Views 732

20.4.3 Storage of Virtual REFs 737

20.4.4 REFs to Nonunique OIDs 737

738

20.5 Not All Views with Objects Are Object Views 738

739

20.6 Schema Evolution 739

741

20.7 Object Views Housekeeping 741

20.7.3 Forcing Compilation 742

743

20.8 Postscript: Using the BFILE Datatype 743

746

21 External Procedures 747

21.1 Introduction to External Procedures 748

21.1.1 Example: Determining Free Disk Space on Windows NT 748

21.1.2 Architecture 750

21.1.3 Advantages 750

21.1.4 Limitations 751

753

21.2 Steps in Creating an External Procedure 753

21.2.1 Step 1: Set Up the Listener 753

21.2.2 Step 2: Identify or Create the Shared Library 755

21.2.3 Step 3: Issue CREATE LIBRARY Statement 755

21.2.4 Step 4: Create the PL/SQL Body 756

21.2.5 Using the rand External Procedure 757

759

21.3 Syntax for External Procedures 759

21.3.1 CREATE LIBRARY: Creating the External Procedure Library 759

21.3.2 EXTERNAL: Creating the PL/SQL Body 760

21.3.3 DROP: Dropping Libraries 761

762xviii

Trang 20

21.4 Mapping Parameters 762

21.4.1 Datatype Conversion 762

21.4.2 More Syntax: The PARAMETERS Clause 764

21.4.3 Properties 765

21.4.4 Correct Declaration of Properties 767

769

21.5 OCI Service Routines 769

770

21.6 External Procedure Housekeeping 770

21.6.2 Rules and Warnings About External Procedures 770

773

21.7 Examples 773

21.7.1 Example: Retrieving the Time Zone 773

21.7.2 Example: Sending Email 776

781

22 Code Design Tips 782

22.1 Select Meaningful Module and Parameter Names 782

22.1.1 Make Sure the Module Name Explains the Module 782

22.1.2 Develop Consistent Naming Conventions for Your Formal Parameters 784

22.1.3 Name Packages and Their Elements to Reflect the Packaged Structure 785

787

22.2 Build the Most Functional Functions 787

22.2.1 Avoid Side Effects in Functions 787

22.2.2 Use a Single RETURN Statement for Successful Termination 790

22.2.3 Avoid Exception Handlers for Normal Program Exits 793

22.2.4 Use Assertion Modules to Validate Parameters and Assumptions 794

798

22.3 Take Full Advantage of Local Modularization 798

801

22.4 Be Wary of Modules Without Any Parameters 801

803

22.5 Create Independent Modules 803

22.5.1 Stretch the Possibilities of the Module 804

22.5.2 Keep the Focus of Your Module 804

22.5.3 Use Parameters Liberally 804

22.5.4 Avoid Global Variables and Data Structures 805

807

22.6 Construct Abstract Data Types (ADTs) 807

22.6.1 Build an ADT in Phases 807

22.6.2 Some ADT Guidelines 808

22.6.3 Progress Box as ADT 808

22.6.4 Price Paid for Code Dispersion 810

814

22.7 Tips for Parameter Design 814

22.7.1 Document All Parameters and Their Functions 814

22.7.2 Use Self−Identifying Parameters (Avoid Boolean Values) 815

22.7.3 Assign Values to All OUT and IN OUT Parameters 816

22.7.4 Ensure Case Consistency of Parameters 818

22.7.5 Default Values and Remote Procedure Calls 820

822

xix

Trang 21

23 Managing Code in the Database 823

23.1 Executing Stored Code 824

23.1.1 Executing Procedures 824

23.1.2 Executing Functions 824

23.1.3 Memory−Based Architecture of PL/SQL Code 825

23.1.4 Key Concepts for Program Execution 826

829

23.2 Transaction Integrity and Execute Authority 829

23.2.1 Execute Authority on Stored Objects 829

23.2.2 Creating Synonyms for Stored Objects 831

832

23.3 Module Validation and Dependency Management 832

23.3.1 Interdependencies of Stored Objects 832

835

23.4 Remote Procedure Calls 835

836

23.5 Managing Stored Objects with SQL*Plus 836

23.5.1 Creating Stored Objects 836

23.5.2 Tips for Storing Code in Files 837

23.5.3 Changing Stored Objects 837

23.5.4 Viewing Compilation Errors in SQL*Plus 839

840

23.6 Using SQL to Examine Stored Objects 840

23.6.1 Displaying Object Dependencies 840

23.6.2 Displaying Information About Stored Objects 841

23.6.3 Analyzing the Size of PL/SQL Code 843

23.6.4 Displaying and Searching Source Code 844

23.6.5 Cross−Referencing Source Code 844

23.6.6 Finding the Code for a Line Number 845

23.6.7 Changing Source Code in the Database 846

848

23.7 Encrypting Stored Code 848

23.7.1 How to Encrypt Code 848

23.7.2 Working with Encrypted Code 849

23.7.3 Impact of Encrypting Code 849

852

24 Debugging PL/SQL 853

24.1 The Wrong Way to Debug 853

24.1.1 Disorganized Debugging 854

24.1.2 Irrational Debugging 854

856

24.2 Debugging Tips and Strategies 856

24.2.1 Gather Data 856

24.2.2 Remain Logical at All Times 857

24.2.3 Analyze Instead of Trying 858

24.2.4 Take Breaks and Ask for Help 859

24.2.5 Change and Test One Area of Code at a Time 859

24.2.6 Document and Back Up Your Efforts 860

24.2.7 Test All Assumptions 861

24.2.8 Leverage Existing Utilities −− Or Build Your Own 862

24.2.9 Build Debugging Messages into Your Packages 863

866xx

Trang 22

25 Tuning PL/SQL Applications 867

25.1 Analyzing Program Performance 867

25.1.1 Use the DBMS_UTILITY.GET_TIME Function 868

871

25.2 Tuning Access to Compiled Code 871

25.2.1 Tune the Size of the Shared Pool of the SGA 87125.2.2 Pin Critical Code into the SGA 87125.2.3 Tune ACCESS$ Table to Reduce First Execution Time of Code 87325.2.4 Creating Packages with Minimal Interdependencies 87425.2.5 Reducing Memory Usage of Package Variables 874

876

25.3 Tuning Access to Your Data 876

25.3.1 Use Package Data to Minimize SQL Access 87625.3.2 Call PL/SQL Functions in SQL to Reduce I/O 87725.3.3 Avoid Client−Side SQL 88025.3.4 Take Advantage of DBMS_SQL Batch Processing 88125.3.5 Avoid Procedural Code When Possible 88125.3.6 Use PL/SQL to Improve Performance of IO−Intensive SQL 88225.3.7 Keep Database Triggers Small 883

886

25.4 Tuning Your Algorithms 886

25.4.1 There Are No Sacred Cows 88625.4.2 Zen and the Art of PL/SQL Tuning 88925.4.3 Rely on Local Variables to Improve Performance 89525.4.4 Use Package Data to Avoid Passing "Bulky" Parameter Values 89825.4.5 Use PLS_INTEGER for All Integer Operations 90025.4.6 Avoid NOT NULL Constraints 90125.4.7 Avoid Type Conversions When Possible 90125.4.8 Use Index−By Tables of Records and Objects 902

903

25.5 Overview of PL/SQL8 Enhancements 903

905

26 Tracing PL/SQL Execution 906

26.1 The PL/SQL Trace Facility 906

26.1.1 Enabling Program Units for Tracing 90626.1.2 Turning On the Trace 90726.1.3 A Sample Tracing Session 908

910

26.2 Tracing for Production Support 910

26.2.1 Features of a Real−Time Support Mechanism 91026.2.2 Starting and Stopping a Support Session 91126.2.3 Filtering Trace Information 912

914

26.3 Free Format Filtering 914

916

26.4 Structured Interface Filtering 916

26.4.1 From Idea to Implementation 916

918

26.5 Quick−and−Dirty Tracing 918

Index 922Table of Contents 922

xxi

Trang 23

Part I: Programming in PL/SQL 922Part II: PL/SQL Language Elements 922Part III: Built−In Functions 922Part IV: Modular Code 922Part V: New PL/SQL8 Features 922Part VI: Making PL/SQL Programs Work 923Part VII: Appendixes 923

923 924

Part I: Programming in PL/SQL 925 926

Part II: PL/SQL Language Elements 927 928

Part III: Built−In Functions 929 930

Part IV: Modular Code 931 932

Part V: New PL/SQL8 Features 933 934

Part VI: Making PL/SQL Programs Work 935 936

Part VII: Appendixes 937 938

Dedication 939 940

Foreword 941 943

Preface 944

Objectives of This Book 946

947

Structure of This Book 947

About the Second Edition 947About the Contents 947

Trang 24

xxiii

Trang 25

1

Trang 26

A What's on the Companion Disk?

Contents:

Installing the Guide

Using the Guide

The content of the companion Windows disk that accompanies this book has been included on this CD, in the

/prog2/disk/ directory It contains the Oracle PL/SQL Programming Companion Utilities Guide, an online tool

designed to help you easily find additional resources The guide offers point−and−click access to nearly 100files of source code and documentation prepared by the authors The goal of providing this material in

electronic form is to give you a leg up on the development of your own PL/SQL programs Providing material

on disk also helps us keep the size of this book under (some) control

A.1 Installing the Guide

In a Microsoft Windows environment, you begin installation by double−clicking on the setup.exe file to run

the installation program If you are working in a non−Windows environment, please visit the RevealNetPL/SQL Pipeline Archives (http://www.revealnet.com/plsql−pipeline) to obtain a compressed file containingthe utilities on this disk

The installation script will lead you through the necessary steps The first screen you will see is the installscreen shown in Figure A.1

Figure A.1: Installing the companion utilities guide

You can change the default directory in which the files will be placed Once this step is compete and thesoftware has been copied to your drive, an icon will appear in the folder you specified Double−click on theicon to start using the Companion Utilities Guide You will then see the main menu shown in Figure A.2

Figure A.2: The main menu

Trang 27

A.2 Using the Guide

The three buttons on the main menu take you to the companion information for this book:

About the Utility Guide

A brief description of the contents of this disk

Package Examples

Extended text and examples that explore the construction of complex packages in PL/SQL FigureA.3 shows buttons available to you for exploration if you choose this Once you select an example,you can scroll through text explaining how the package was designed and built You can also choose

to view the package specification and body, and copy either to the clipboard

Figure A.3: The package examples

Source Code Index

The guide gives you point−and−click access to each of the files on the companion disk The files arelisted in chapter order to make it easy for you to move between the book and guide Source codelistings in the book begin with comment lines keyed to the filenames on the disk Figure A.4 shows aportion of the Source Code Index

Figure A.4: The Source Code Index

Procedures from PL/SQL

3

Trang 28

Version 1.1

4

Trang 29

5

Trang 30

B Calling Stored Procedures from PL/SQL Version 1.1

Contents:

Using Stubs to Talk to Server−Side PL/SQL

Restrictions on Calling Stored Procedures

The Oracle Developer/2000 tools use PL/SQL Version 1.1, while the PL/SQL versions on the server rangefrom 2.0 to 8.x The PL/SQL version inside the Oracle Developer/2000 tools will be upgraded to PL/SQLRelease 2.3 sometime in 1998 with Release 2 of Oracle Developer/2000 In the meantime, the tools group atOracle Corporation has had to come up with a way to allow applications based on Oracle Developer/2000 tocall stored procedures in the most transparent fashion possible The end result is a mechanism which:

Does not require any special syntax to distinguish between stored and local PL/SQL modules

Achieving this effect, however, imposes several restrictions on the use of stored procedures:

•

You cannot look up a remote subprogram via a synonym until RDBMS Version 7.1.1

Trang 31

B.1 Using Stubs to Talk to Server−Side PL/SQL

The mechanism employed by the Oracle Developer/2000 tools to handle stored procedures is called stubgeneration A stub is a PL/SQL procedure or function which has the same header as the actual procedure orfunction A stub for a package contains a stub or specification for each module in the package

When the Oracle Developer/2000 tool encounters an identifier in a PL/SQL code segment, it checks to see if it

is a local PL/SQL variable, then a tool bind variable, table/view, synonym, sequence, and so on through theprecedence order of object name resolution If it is unable to resolve the reference, the PL/SQL compiler calls

a stub generator to see if it can resolve the identifier as a stored function or procedure In that case, a stub isgenerated for syntactical checking, and the compiler continues Because the stub looks the same to the OracleDeveloper/2000 tool as the stored module, the tool can continue to perform syntactical checks using that stub.Stub generation only occurs at compile time

You can see what kind of stub PL/SQL generates in the Oracle Developer/2000 tool by executing the stubgenerator directly from SQL*Plus, as shown below:

VARIABLE not_needed VARCHAR2(2000);

VARIABLE stubtext VARCHAR2(2000);

DELETE FROM SYS.PSTUBTBL;

EXECUTE SYS.PSTUB ('&1', NULL, :not_needed, :stubtext);

PRINT stubtext;

DELETE FROM SYS.PSTUBTBL;

where "&1" is a substitution variable Notice that I delete from the stub table, SYS.PSTUBTBL, before andafter my call to the SYS pstub generator program This is a temporary table and must be cleaned up manually

if you are going to call the PSTUB program yourself

Place this code in a file named showstub.sql and you can then call it as follows to show a module's stub:

SQL> start showstub calc_totals

The following is an example of the output from this showstub program:

SQL> CREATE PROCEDURE calc_totals

SQL> (company_id_in IN NUMBER, type_inout IN OUT VARCHAR2)

procedure calc_totals (COMPANY_ID_IN NUMBER, TYPE_INOUT in out CHAR) is

begin stproc.in('begin calc_totls(:COMPANY_ID_IN, :TYPE_INOUT); end;');

stproc.bind_i(COMPANY_ID_IN); stproc.bind_io(TYPE_INOUT);

stproc.execute;

stproc.retrieve(2, TYPE_INOUT); end;

If the output from showstub is `$$$ s_notv6Compat', you may be trying to use parameters with the %TYPEattribute, which are not allowed in the parameter list of a stored procedure called from Oracle Developer/2000tools If the output is `$$$ s_subp not found', the problem is that the stub generator cannot find the module.This will happen if you have not created a synonym for a module which is owned by another user The stubgenerator cannot search across different users to resolve a named object reference You will have to create a

Trang 32

public synonym for this module and then grant EXECUTE authority on that module to PUBLIC.

Stored Procedures

Trang 33

from PL/SQL Version 1.1

B.2 Restrictions on Calling Stored Procedures

It's good to know why and how the Oracle Developer/2000 tools make stored procedures available, but therestrictions on use of those objects has the most direct impact on developers Let's examine each restrictionand the steps you can take to work around those restrictions

B.2.1 No Server−Side PL/SQL Datatypes

Parameters in stored procedures, as well as the RETURN datatype of stored functions, can only have one ofthese datatypes if they are to be used by Oracle Forms This rule applies both to standalone and packagemodules Remember: when you work in a Oracle Developer/2000 tool, you are using PL/SQL Version 1.1;any code you write, including calls to stored modules, must conform to Version 1.1 compiler syntax rules.The specification or "public" side of a stored module must look like a Version 1.1 module Behind the

specification −− in other words, the implementation of that module −− can have all the server−side PL/SQLfeatures you can pack into it You just can't let any of that show outside of the body of the module or package.Suppose you define a stored procedure as follows:

FUNCTION get_row RETURN BINARY_INTEGER;

If you try to execute the function inside an Oracle Forms PL/SQL block, the compiler will tell you:

Identifier 'GET_ROW' must be declared

It literally cannot even find a match for the function if the datatype does not conform to PL/SQL Version 1valid datatypes The SYS.PSTUB procedure will have been unable to generate a stub and so the name remainsunresolved

There are two ways to work around this problem:

no other options

In many situations, you won't have the opportunity to change the specification (parameter list) of a storedmodule It will have been written by others, perhaps for another application, and cannot be modified without

9

Trang 34

possibly affecting those other applications.

In this case, the second workaround is annoying but thoroughly able to be implemented If your Oracle

Developer/2000 code must call the get_row function, for example, you can create another stored object (let'scall it Oracle Developer/2000_get_row) which does not return a BINARY_INTEGER, but instead returns aNUMBER The specification and body for Oracle Developer/2000_get_row would be:

FUNCTION Oracle Developer 2000_get_row RETURN INTEGER IS

B.2.2 No Direct Stored Package Variable References

This is the most serious drawback of the implementation for accessing stored objects from Oracle

Developer/2000 You simply cannot use the dot notation to reference a package variable, whether it be astring, exception, or cursor Consider the pet maintenance package which we discussed earlier in this book

FUNCTION next_pet_shots (pet_id_in IN NUMBER) RETURN DATE;

PROCEDURE set_schedule (pet_id_in IN NUMBER);

PROCEDURE check_activity (pet_id_in IN NUMBER);

END pet_maint;

You can call the modules using dot notation, as in:

pet_maint.check_activity (1503);

but you cannot make reference to any of the package variables using this same dot notation All of the

statements shown in boldface will fail to compile:

Trang 35

pet_maint.max_pets_in_facility in their code, you can never change how you store that value If you hide itbehind modules, you could decide to store that value in a PL/SQL table or record and not have any impactoutside of the package.

The following example shows a new specification for the pet_maint package In this version the

max_pets_in_facility variable has been moved to the body of the package and is replaced by the get_max andset_max modules

FUNCTION get_max_pets RETURN INTEGER;

PROCEDURE set_max_pets (max_in IN INTEGER);

FUNCTION next_pet_shots (pet_id_in IN NUMBER) RETURN DATE;

PROCEDURE set_schedule (pet_id_in IN NUMBER);

PROCEDURE check_activity (pet_id_in IN NUMBER);

|| Fetch next record from the cursor Also set a status variable

|| to indicate if a record was fetched (corresponds to

|| the %FOUND attribute).

*/

IS

BEGIN

FETCH pet_maint.pet_cur INTO pet_rec_out;

Trang 36

user−defined exception number between −20000 and −20999.

B.2.3 No Direct Remote Procedure Calls

This very powerful feature is unavailable from Oracle Developer/2000 Instead, you will have to create asynonym for the remote procedure and then execute the synonym rather than the procedure directly (Don'tforget to grant EXECUTE authority on the synonym!)

Suppose I want to execute the following procedure from an Oracle Forms application:

Grant EXECUTE authority on that synonym:

GRANT EXECUTE ON HQ_new_schedule TO <user_or_role>;

3

Call the synonym in my Oracle Forms trigger or program unit:

HQ_new_schedule;

B.2.4 No Default Parameter Values

PL/SQL Version 2.0 does not allow you to use default parameter values when you are performing a remoteprocedure call (You must leave any arguments which have default values in the specification out of themodule execution.) Even if you do not append an @ symbol on a call to a stored procedure, PL/SQL doesconsider that a remote procedure call because the client−side application is "remote" from the server

Trang 37

Unfortunately, if you do try to call a stored object from a Oracle Developer/2000 component and rely on adefault value, the PL/SQL error does not offer much help It will not ask you to include values for all

parameters It will simply tell you:

Error at line N:

Identifier 'STORED_OBJECT' must be declared

The first time I encountered this error, I panicked Why couldn't Oracle Forms find the stored procedure? Ilogged in through SQL*Plus and could run the module there So I knew it was defined and stored in thedatabase Was it a security issue within Oracle Forms? Did I have to do something special to get Oracle Forms

to realize it was looking for a stored object and not a local program unit? In the end, I discovered that OracleForms could find the object, it just couldn't use it (create a stub for it) because I hadn't passed the full set ofarguments

So when your Oracle Developer/2000 PL/SQL compiler tells you that an identifier "must be declared", makesure you that you included an argument for each parameter in the stored module parameter list You shouldnot consider this too much of a hardship; good programming practice dictates that you never rely on thedefault values anyway

B.1 Using Stubs to Talk to

Server−Side PL/SQL

C Built−In Packages

Trang 38

Appendix C

14

Trang 39

Table C.1: Built−In Packages Stored in the Oracle Database

Registers a process with an alert and then waits for a signal from that alert

(PL/SQL8 only)

(PL/SQL Release 2.1)

shared memory

for conversion between restricted and extended ROWIDs (PL/SQL8 only)

commands and other session−level commands

Trang 40

DBMS_SNAPSHOT Provides a programmatic interface through which you can manage snapshots

and purge snapshot logs You might use modules in this package to build scripts

to automate maintenance of snapshots

statements that are not prewritten into your programs They are, instead,constructed at run time as character strings and then passed to the SQL enginefor execution (PL/SQL Release 2.1)

DBMS_ TRANSACTION Provides a programmatic interface to a number of the SQL transaction

statements, such as SET TRANSACTION

FORMAT_CALL_STACK, which returns the current stack of called modules

(PL/SQL Release 2.3)All of the packages in Table C.1 are stored in the database and can be executed both by client− and

server−based PL/SQL programs In addition to these packages, many of the development tools, like OracleForms, offer their own specific package extensions, such as packages to manage OLE2 objects and DDEcommunication.[1]

[1] For more detailed information about these built−in packages, see my book, Oracle

Built−in Packages

C.1 Using the Built−in Packages

In this appendix, I've provided a brief overview of each package, followed by a description and header foreach program in the package These headers are structured as follows:

PROCEDURE pkg.procname (<parameter list>);

FUNCTION pkg.funcname (<parameter list>) RETURN <return datatype>;

where pkg is the name of the package, procname and funcname are the names of the programs, <parameterlist> is the list of parameters (if there are no parameters, then you do not provide parentheses either) and

<return datatype> is the datatype of the value returned by the function

Let's look at an example Suppose that you want to receive a message from a pipe The header for the built−infunction which does this is:

When I want to call a packaged program, I must use dot notation For example to make use of the

RECEIVE_MESSAGE built−in, I would write code like this:

DECLARE

pipe_status INTEGER;

BEGIN

pipe_status DBMS_PIPE.RECEIVE_MESSAGE (mypipe, 10);

Tiêu đề	Oracle PL/SQL Programming
Thể loại	tài liệu

Định dạng
Số trang	984
Dung lượng	3,15 MB