P2 oracle SQL

Nguyễn Thị Hải Bình Khoa Công nghệ thông tin Đại học Giao thông Vận tải... Nguyễn Thị Hải Bình Type of SQL Statements Three essential categories • Data Definition Language DDL Statements

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ORACLE SQL

GV Nguyễn Thị Hải Bình Khoa Công nghệ thông tin Đại học Giao thông Vận tải

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Công nghệ Oracle

GV Nguyễn Thị Hải Bình

Type of SQL Statements

Three essential categories

• Data Definition Language (DDL) Statements

• DDL allows you to create, modify, and remove database objects.

• Data Manipulation Language (DML) Statements

• DML is used to manipulate data.

• SELECT

• Is used to retrieve data from Oracle Database objects.

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SQL Tools

SQL*Plus Command Line

Start up SQL*Plus Command Line

• Open command-line prompt (cmd)

• Type: sqlplus sys/pwd as sysdba

or sqlplus system/pwd

Exit SQL*Plus

• Type: exit

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Object Context Menu

• Right-click on an object to display its

“Context Menu”

• Edit option: view/modify the table

definition.

• Other options open additional menus

allowing the user to issue commands graphically.

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Oracle’s naming standards

• The name should be 1 to 30 characters long

• The name is interpreted as uppercase (unless enclosed

in double quotes)

• The name must begin with a letter

• The name contains only letters, numbers, or thesethree symbols: $, #, _ (unless enclosed in doublequotes)

• If enclosed in double quotes, a column name

• is case sensitive

• can begin with any character

• include any letter, number, space character or symbol

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• A column defined as NUMBER(n, m)

• can have a maximum of (n-m) digits before the decimal point and m digits after the decimal point.

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• Stores alphanumeric data.

• Is the variable-length data type

BLOB

• Stores one value up to four gigabytes in size

• Usually reserved for multimedia applications such asstoring a video or audio file

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THE SELECT STATEMENT

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• What types of SELECT statements are possible?

• What else is interesting about SELECT statements?

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Simple Query

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Tips on writing good queries

• Use table alias

• Be careful with parentheses

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Tips on writing good queries

• Upper and lowercase make no difference so long as

they are not in quotation marks

• When enclosed in quotation marks (single or double),

then upper and lowercase are considered different.

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Simple WHERE clause examples

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Top – N Queries

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Sorted Query

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Sorting and Null Values

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Using DISTINCT

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• The NVL (value, replace) function replaces null values

in expressions, avoiding SQL errors The SET NULLenvironment variable does the same thing in SQL*Plus

• Null values sort as the highest value by default

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Arithmetic Operators

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Logical Operators

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ROW FUNCTIONS

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• A function always returns a single value.

• You can call a function within a query or other SQLcommand

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Type of Functions

Single – row functions

• Functions that operate on a single row at a time

Grouping functions

• Aggregate Functions Functions that operate on a

group of rows at one time and return a single row

• Analytical Functions Functions that operate on groups

of rows and return one or more summary rows

Object Reference Functions

• Functions that manipulate the value in columns withthe REF datatype in object tables

User-Defined Functions.

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Single-row Functions

String Functions

INSTR(expression, substring [, p [, i]])

• Returns the position of a substring within a string

• The position and occurrence parameters are optional

• The p parameter determines a start point to search

from

• If p<0, search from right to left.

• The i parameter indicates which duplicate, if any, of the

substring should be matched

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• Left or right pad a string from the left or the right (start

or end of the string) with the specified characters inthe second string, up to a string length of n characters

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SQL> select rtrim('test2101','1') from dual

SQL> select rtrim('test2101','10') from dual;

SQL> select rtrim('test2101','2') from dual;

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String Functions

REPLACE(expression, search [, replace])

• REPLACE will replace every occurrence of the searchstring with the replacement string

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String Functions

TRANSLATE(expression, search [, replace])

• TRANSLATE function replaces a sequence of characters

in a string with another set of characters

• However, it replaces a single character at a time

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String Functions

SUBSTR(expression, [-]position[, length])

• The SUBSTR function returns a portion of a string

• If the length parameter is omitted, then all charactersafter the value of position are returned

• If the position parameter is positive, then the substringvalue is extracted from the left of the string

• If the parameter is negative, the value is extracted fromthe right (end) of the string

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Datatype Conversion Functions

Number Conversion Functions

• TO_CHAR(number[, format]): convert a number to astring

• TO_NUMBER(string [, format]):convert a string to anumber

Date Conversion Functions

• TO_CHAR(date[, format]): Converts a date to a string

• TO_DATE(string [, format]): Converts a stringrepresentation of a date to a date

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Miscellaneous Functions

DECODE( expression , compare_value, return_value,

[,compare, return_value] [,default_return_value] )

with:

• expression is the value to evaluate

• compare_value is the value that can match the

evaluated value

• return_value is the value that is returned if

compare_value equals the value

• The default_return_value is the value that is returned if

no match is found

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Miscellaneous Functions

DECODE( expression , compare_value, return_value,

[,compare, return_value] [,default_return_value] )

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,'Harry','It is Harry!' ,'Joe','It is Joe!‘

,'Not Harry or Joe.')

DECODE('Joe'

,'Harry','It is Harry!' ,'Joe','It is Joe!'

DECODE('Mary'

,'Harry','It is Harry!' ,'Joe','It is Joe!'

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Combining Functions

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Combining Functions

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JOINING TABLES

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Natural Join (Inner Join)

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suppliers orders

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Left Outer Join

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suppliers orders

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Right Outer Join

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Full Outer Join

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GROUP BY

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Group By

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Analytic Functions

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Analytic Functions

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Query_partition_clause

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Order_by_clause

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ROLLUP and CUBE Clause

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A simple example

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Types of Subqueries

Based on what they return

• Single row/single column

• Multiple Rows / One Column Each

• Multiple Columns / Single or Multiple Rows

Based on the connection between calling and called queries (subqueries)

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Comparison Conditions and Subqueries

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ORDER BY in Composite Queries

• The ORDER BY clause is applied to all rows returned inthe final result set

• Columns in the ORDER BY clause can be referenced bycolumn names or column aliases present in the firstquery of the statement

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[START WITH initial_condition]

CONNECT BY [nocycle] PRIOR recurse_condition

[ORDER SIBLINGS BY order_by_clause]

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CONNECT BY example

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LEVEL example

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START WITH and ORDER BY example

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START WITH and ORDER BY example

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Loop in data

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Loop in data

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CONNECT_BY_ISCYCLE pseudocolumn

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CONNECT BY ROOT example

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GROUP BY

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Regular Expressions

• Regular expressions enable you to search for patterns

in string data by using standardized syntax conventions

Regular Expression Functions

• REGEXP_INSTR( string, pattern [, start_position [,

th_appearance [, return_option [, match_parameter ] ] ] ] )

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Regular Expressions

• REGEXP_SUBSTR( string, pattern [, start_position [,

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Regular Expressions

• REGEXP_REPLACE( string, pattern [, replacement_string[, start_position [, th_appearance [, match_parameter ] ] ] ] )

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Regular Expressions

• REGEXP_LIKE( string, pattern [, match_parameter ] )

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DATA MANIPULATION

LANGUAGE (DML)

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INSERT Statement - Example

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UPDATE Statement

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UPDATE Statement - Example

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UPDATE Statement – Example …

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UPDATE Statement – Example …

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DELETE Statement

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DELETE Statement - Examples

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DELETE Statement - Examples

• How would I write an Oracle DELETE statement todelete all records in TableA whose data in field1 &field2 DO NOT match the data in fieldx & fieldz ofTableB?

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TRUNCATE TABLE Statement

• Is used to remove all records from a table

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MERGE Statement

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MERGE Statement

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MERGE Statement

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MERGE Statement – WHERE clause

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MERGE Statement – DELETE clause

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MERGE Statement – DELETE clause…

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XML IN ORACLE

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CREATE TABLE Statement

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CREATE TABLE AS Statement

• Is used to create a table from an existing table bycopying the existing table’s columns

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CREATE TABLE AS Statement - Examples

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Primary Key

• A primary key is a single field or combination of fields that

uniquely defines a record.

• None of the fields that are part of the primary key can contain a null value.

• A table can have only one primary key.

• In Oracle, a primary key can not contain more than 32 columns.

• A primary key can be defined in either a CREATE TABLE statement or an ALTER TABLE statement.

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Primary Key - Examples

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Create A Primary Key – ALTER TABLE statement

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Drop/ Disable/ Enable A Primary Key

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Create A Foreign Key

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Create A Foreign Key - Examples

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Foreign Keys with cascade delete

• A foreign key with cascade delete means that if arecord in the parent table is deleted, then the

automatically be deleted

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Foreign Keys with cascade delete

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Foreign Keys with set null on delete

• A foreign key with "set null on delete" means that if arecord in the parent table is deleted, then thecorresponding records in the child table will have theforeign key fields set to null

• The records in the child table will not be deleted

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Foreign Keys with set null on delete

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Drop/ Disable/ Enable A Foreign Key

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Unique Constraints

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Drop/Disable/Enable A Unique Constraint

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• A check constraint can NOT include a SQL Subquery.

• A check constraint can be defined in either a SQL

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Check Constraints - Syntax

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Check Constraints - Examples

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Drop/ Disable/ Enable A Check Constraint

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Changing Table Structure

Table changes

• Change the name of a table

Adding or changing columns

• Change the datatype, length, or name of columns

Removing columns

• Remove a column and its data

Rebuilding tables

• Reordering the columns in a table

• Adding columns between existing columns

• Change the primary key of a table

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RENAME old_name TO new_name;

ALTER TABLE old_name TO new_name;

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Add Columns in a Table

Add multiple columns in a table

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Modify Columns in a Table

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Drop/Rename a Column

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CREATE VIEW Statement

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Update View

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Drop View

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Question?

• Can you update the data in an Oracle VIEW?

• Does the Oracle View exist if the table is dropped fromthe database?

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