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SQL

Structured Query Language

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Structured Query Language

• Data Definition Language (DDL) is used to manage table and define data structure i.e. CREATE, ALTER, DROP

• Data Control Language (DCL) is used to control user’s privilege on accessing data i.e. GRANT, REVOKE

• Data Manipulation Language (DML) is used to manage data record i.e. ADD, UPDATE, and DELETE.– This may include SELECT but it may be consider as a member of Data

Query Language (DQL)

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Browsing Databases

• Some useful commands to begin with– show databases; – use <database_name>; – show tables;– desc <table_name>;– create database <database_name>;

• Create a new database

CREATE DATABASE BangNa;

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Create a Table

CREATE TABLE std_phone (STD_ID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,FNAME VARCHAR (64) NOT NULL ,LNAME VARCHAR(64 ) NOT NULL ,PHONE VARCHAR(12) NOT NULL

)

CREATE TABLE <table_name> (column_name1 <col_type> ….., ............column_name2 <col_type> ….., ............………………………..

)

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Create a User

• It is a good idea to create a username to manage tables in new created database

• Proper privileges can be granted to a particular user so that only a user who has right access can manage the table

GRANT <previledge> [(col1, col2, … colN)] ON database.[table] TO user@host IDENTIFIED BY 'passwd';

GRANT select ON webtech.student_profile TO tct IDENTIFIED BY ‘tct';

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SELECT Statements

• Select all records (rows) from a table

• Select some columns of all records from a table

SELECT * FROM <table_name>;

SELECT col1, col2,….coln FROM <table_name>;

SELECT * FROM std_phone;

SELECT std_id, fname, lname FROM std_phone;

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SELECT Statements (cont.)

• Select some records from a table

• WHERE clause could be any boolean expression

SELECT * FROM std_phone WHERE std_id < 20;

SELECT * FROM <table_name> WHERE <condition>;

SELECT * FROM std_phone WHERE std_id < 20 AND fname like ‘sor%’;

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INSERT INTO

• Insert a record into a table

• Insert record(s) from a table right into another table

INSERT INTO table (col1, col2, col3) VALUES(val1, val2, val3);

INSERT INTO std_phone (fname, lname, phone) VALUES(“Khaosai”, “Galaxy”, “088-123-4567”);

INSERT INTO std_phone (fname, lname, phone) select fname, lname, phone from std_profiles

where academic_year = ‘2552’;

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Edit a Record

• Modify a record

• Modify Khaosai’s phone number

UPDATE <table> SET field1=’val1’, field2=’val2’, field3=’val3’ WHERE <condition>;

UPDATE std_phone SET phone=‘089-123-1234’

WHERE fname = ‘Khaosai’ AND lname = ‘Galaxy’;

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Delete Record(s)

• Delete selected record(s)

• Delete Khaosai’s record from the table

– This will delete all records with firstname ‘Khaosai’

– This will delete all records with lastname ‘Galaxy’

DELETE FROM <table> WHERE <condition>;

DELETE FROM std_phone WHERE fname = ‘Khaosai’;

DELETE FROM std_phone WHERE lname = ‘Galaxy’;

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Delete Record(s)

• Do a better job with AND

– Anyway, this would be a better choice by using primary key to locate the target record to be deleted.

• Note: avoid this;

– it will delete all records in the tatble

DELETE FROM std_phone WHERE std_id = 20;

DELETE FROM std_phone WHERE fname = ‘Khaosai’

AND lname = ‘Galaxy’;

DELETE FROM std_phone;

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