slide môn học MySQL bài 4 implementing the SQL queries using MySQL II

MySQL Database / Session 8 / Slide 2 of 18 MySQL list of databases in the server with the help of SHOW command  The ALTER command enables us to modify the characteristics or attribute

Implementing the SQL Queries using

MySQL - II

Session 8

MySQL Database / Session 8 / Slide 2 of 18

 MySQL list of databases in the server with

the help of SHOW command

 The ALTER command enables us to modify the characteristics or attributes of a table or

a database

 The SELECT command is used for data retrieval

 The DROP command is used to remove or delete

a table from a database This command removes all data from that table along with the table definition from the database

Review

 Work with keys

 Work with indexes

 Manipulate tables

 Control the output using ORDER BY

clause

 Organize the output using the

GROUP BY command

MySQL Database / Session 8 / Slide 4 of 18

Working with Keys and Indexes - I

 Indexes are used to improve the overall performance of a database

 Enables the searches on a database to be faster

 MySQL allows up to 32 indexes for each table

 Each index may consists up to 16 columns

 Advantages of indexing:

 Searching is faster

 Sorting is faster

 Indexing causes the process of altering database to be slower

Working with Keys and Indexes - II

 The syntax for creating an index for a table is:

CREATE INDEX index_name ON tablename

(column1,column2, , columnN)

 To create an index INDEX1 on

EMP_DEPARTMENT, enter the

following at the command prompt:

CREATE INDEX INDEX1 ON

EMP_DEPARTMENT(DATE_OF_JOI

MySQL Database / Session 8 / Slide 6 of 18

Defining Keys - I

 Keys are columns that helps to

identify a record in a table

 Primary key is a unique identifier in

a table

 Foreign key is a column in a table is

a primary key in a different table

 In order to define a foreign key both

the table must of the type InnoDB

Defining Keys - II

 To add the foreign key, enter the

following at the command prompt:

ALTER TABLE EMP_SALARY ADD FOREIGN KEY

(E_ID) REFERENCES EMP_DETAILS;

MySQL Database / Session 8 / Slide 8 of 18

Manipulating the Tables

 INSERT command is used to data in a

table

 The command for the INSERT command

is:

INSERT [LOW_PRIORITY | DELAYED] [IGNORE]

[INTO] tbl_name [(col_name, )] VALUES

({expression | DEFAULT}, ),( ), [ON

DUPLICATE KEY UPDATE col_name = expression

, ]

INSERT Command

 To insert rows in EMP_DEPARTMENT, enter

the following at the command prompt:

INSERT INTO EMP_DEPARTMENT VALUES

(101,’MARKETING’,’2000-05-15’,A01’);

MySQL Database / Session 8 / Slide 10 of 18

UPDATE Command

 To update a row in

EMP_DETAILS table,

enter the following at

the command prompt:

UPDATE EMP_DETAILS SET

EMAIL_ID=’peter102@cbase.

com’WHERE E_ID=102;

 The syntax for updating a table is:

UPDATE [LOW_PRIORITY] [IGNORE] table SET

column=value, [WHERE clause][LIMIT n]

REPLACE Command

 The syntax for deleting from a table is:

REPLACE [DELAYED|LOW_PRIORITY] INTO table

[(column,…)] VALUES (value, )

 To update a row in EMP_DETAILS

table, enter the following at the

command prompt:

REPLACE INTO EMP_DETAILS

VALUES

MySQL Database / Session 8 / Slide 12 of 18

DELETE Command

 To delete a row from the

EMP_DETAILS table, enter

the following at the

command prompt:

DELETE FROM EMP_DETAILS

WHERE E_ID=106;

 DELETE command is used to delete a row from a table

 Syntax for deleting from a table is:

DELETE [LOW_PRIORITY|QUICK] FROM table

[WHERE clause] [ORDER BY column, ]

[LIMIT n]

Using the ORDER BY Clause – I

 ORDER BY Clause is used to sort the

table

 The syntax for 0RDER BY is:

ORDER BY column [ASC|DESC]

[,column2[ASC|DESC], ]

 If the ASC or DESC option is not

specified then by default the output

MySQL Database / Session 8 / Slide 14 of 18

Using the ORDER BY Clause – II

 To order the output

DATE_OF _JOIN field

in the ascending

order, enter the

following at the

command prompt:

SELECT * FROM

EMP_DEPARTMENT

ORDER BY

DATE_OF_JOIN ASC;

Using the GROUP BY Command - I

 Grouping facilitates the user to group

rows with similar values for a

specific column into a single row in

order to operate on them together

 The syntax for ordering is:

GROUP BY column [,column2 ]

MySQL Database / Session 8 / Slide 16 of 18

Using the GROUP BY Command - II

 To group the output

of EMP_DEPARTMENT

table on the

DESIGNATION field,

enter the following

at the command

prompt:

SELECT * FROM

EMP_DEPARTMENT GROUP

BY DESIGNATION;

Summary - I

 Keys uniquely identify a record in a table

 Primary key is a unique identifier in a

table

 Foreign key is a primary key in a

different table

 We can define a primary key as well as

foreign key while creating a table

 We also define these keys using the ALTER

MySQL Database / Session 8 / Slide 18 of 18

Summary - II

 UPADTE command is used to modify data in

a table

 REPALCE command is used to change data in

a table

 DELETE command enables user to delete the data from a table

 ORBER BY option is used with the select

command to order the output

 Grouping facilitates to group rows with

similar values for a specific column into

a single row