SQL Unit – 2 Base Knowledge Presented By Mr. R.Aravindhan

SQL SQL is a standard language for accessing and manipulating databases.

What is SQL? SQL stands for Structured Query Language SQL lets you access and manipulate databases SQL is an ANSI (American National Standards Institute) standard

What Can SQL do? SQL can execute queries against a database SQL can retrieve data from a database SQL can insert records in a database SQL can update records in a database SQL can delete records from a database SQL can create new databases SQL can create new tables in a database

What Can SQL do? SQL can create stored procedures in a database SQL can create views in a database SQL can set permissions on tables, procedures, and views

SQL DML and DDL SQL can be divided into two parts: The Data Manipulation Language (DML) and the Data Definition Language (DDL).

DML The query and update commands form the DML part of SQL: SELECT - extracts data from a database UPDATE - updates data in a database DELETE - deletes data from a database INSERT INTO - inserts new data into a database

DDL CREATE DATABASE - creates a new database ALTER DATABASE - modifies a database CREATE TABLE - creates a new table ALTER TABLE - modifies a table DROP TABLE - deletes a table CREATE INDEX - creates an index (search key) DROP INDEX - deletes an index

SQL SELECT Statement Syntax SELECT column_name(s) FROM table_name Example SELECT LastName,FirstName FROM Persons

SQL SELECT DISTINCT Statement Syntax SELECT DISTINCT column_name(s) FROM table_name Example SELECT DISTINCT City FROM Persons

SQL WHERE Clause Syntax: SELECT column_name(s) FROM table_name WHERE column_name operator value Example: SELECT * FROM Persons WHERE City='Sandnes'

SQL ORDER BY Keyword Syntax: SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC Example: SELECT * FROM Persons ORDER BY LastName

SQL INSERT INTO Statement Syntax: INSERT INTO table_name VALUES (value1, value2, value3,...) Example: INSERT INTO Persons VALUES (4,'Nilsen', 'Johan', 'Bakken 2', 'Stavanger')

SQL UPDATE Statement Syntax: UPDATE table_name SET column1=value, column2=value2,... WHERE some_column=some_value Example: UPDATE Persons SET Address='Nissestien 67', City='Sandnes' WHERE LastName='Tjessem' AND FirstName='Jakob'

SQL DELETE Statement Syntax: DELETE FROM table_name WHERE some_column=some_value Example: DELETE FROM Persons WHERE LastName='Tjessem' AND FirstName='Jakob'

Thank You