DML Commands - Insert - Update - Delete in SQL

                                       Data Manipulation Language (DML)

DML is the second sub-language in SQL which is used to manipulate the data with in the table.This language contains 3 commands

                                * Insert

                                * Update

                                * Delete

Note: 

Except Truncate all DDL commands will works on structure of the table.

All DML commands will works on DATA in the table .

Insert:

                This command is used to insert the records into the existing table. using this method we can insert the data into the table in 2 methods

                * Explicit Method                                             * Implicit Method

Explicit Method:

                In this method the user has to enter all the values into all columns without omitting any column data i.e nof columns=nof rows

Syntax: 

              Insert  <Table Name> values (CN1,CN2,CN3.........)

Ex:        

              Insert into emp values(101,'sai',37400)

Note: 

         

         In SQL Server into keyword is an optional during insertion .

Implicit Method :

                In this method we can enter values at required columns in the table. So that the user has the facility to enter the values in a specific column. If you donot enter the values in any particular column that column automatically takes NULL.NULL is not equals to zero and NULL is not equal to Space

Syntax: 

             Insert into <Table Name> (CN1,CN2) values(value1,value2)

Ex: 

           Insert into emp (empid,ename) values(1001,'optimize)

Update :

              Update command is used to update 1/more records in an existing table

Syntax: 

            

             Update <Table Name> set columname=value where <condition>

Ex: 

            Update emp set sal=4500 where ename='optimize'

NOTE: 

You can use update command without where clause , by writing update command in this method all records are updated  at a time it is meaning less

Delete :

This command is used to delete 1/more or all records at a time from an existing table

Syntax to delete all records at a time

Delete from <Table Name> 

Syntax to delete only one record at a time

Delete from <Table Name> where <condition>