365edu: SQL Data Manipulation Language (DML)

SQL Tutorial
SQL BASICS
o	SQL INTRODUCTION
o	SQL STATEMENTS
o	SQL DISTINCT Statement
o	SQL WHERE Clause
o	SQL LIKE Condition



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SQL - (Structured Query Language)

SQL Data Manipulation Language (DML)

SQL (Structured Query Language) is a syntax for executing queries. But the SQL language also includes a syntax to update, insert, and delete records.

These query and update commands together form the Data Manipulation Language (DML) part of SQL:

SELECT - extracts data from a database table
UPDATE - updates data in a database table
DELETE - deletes data from a database table
INSERT INTO - inserts new data into a database table

SQL Data Definition Language (DDL)

The Data Definition Language (DDL) part of SQL permits database tables to be created or deleted. We can also define indexes (keys), specify links between tables, and impose constraints between database tables.

The most important DDL statements in SQL are:

CREATE TABLE - creates a new database table
ALTER TABLE - alters (changes) a database table
DROP TABLE - deletes a database table
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index

The SQL SELECT Statement

The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result-set).

Syntax

SELECT column_name(s)

FROM table_name

Note: SQL statements are not case sensitive. SELECT is the same as select.

SQL SELECT Example

SELECT LastName,FirstName FROM Persons

The database table "Persons":

LastName	FirstName	Address	City
Koteswara Rao	Parala	Chimakurthy	Ongole
Raja Ramesh	Prathiwada	Nellore	Nellore
Ashok	Kosuri	Nellore	Nellore
Vivek	Chavanaboina	Nellore	Nellore
Abbas	MD	Maddipadu	Ongole

The result

LastName	FirstName
Koteswara Rao	Parala
Raja Ramesh	Prathiwada
Ashok	Kosuri
Vivek	Chavanaboina
Abbas	MD

Select All Columns

To select all columns from the "Persons" table, use a * symbol instead of column names, like this:

SELECT * FROM Persons

Result

LastName	FirstName	Address	City
Koteswara Rao	Parala	Chimakurthy	Ongole
Raja Ramesh	Prathiwada	Nellore	Nellore
Ashok	Kosuri	Nellore	Nellore
Vivek	Chavanaboina	Nellore	Nellore
Abbas	MD	Maddipadu	Ongole

The Result Set

The result from a SQL query is stored in a result-set. Most database software systems allow navigation of the result set with programming functions, like: Move-To-First-Record, Get-Record-Content, Move-To-Next-Record, etc.

Programming functions like these are not a part of this tutorial. To learn about accessing data with function calls, please learn ADO tutorial.

Semicolon after SQL Statements?

Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.
Some SQL tutorials end each SQL statement with a semicolon. Is this necessary? We are using MS Access and SQL Server 2000 and we do not have to put a semicolon after each SQL statement, but some database programs force you to use it.