Monday, 8 July 2013

DDL,DML,DCL,TCL

SQL SERVER  - DML, DDL, DCL and TCL Introduction 

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DDL

DDL is the abbreviation of Data Definition Language, It is used to create , modify and drop the Database objects.
Examples : CREATE, ALTER, DROP statements

Let we consider the Database objects : Table,View

Table 
CREATE TABLE Emploee
(
     id           int    identity(1,1),
     name     varchar(40)  ,
     age        int
)

In the above example, we are creating a table and save the object to database. Table have columns id,name,age  which are in data type int,varchar(40),int . Column id set a Identity that means each value in that column in unique starts with 1 and increment by 1 so we don't need to insert the value for this column . value is automatically inserted by Sql Server. varchar datatype is representing the string type with 40 length

ALTER TABLE Employee
ALTER  address varchar(100)

In the above example, additional column address is added to the existing table Employee . Column address is defined as varchar(100)

DROP TABLE Employee

In the above example, Employee table is dropped from database

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DML

DML is the abbreviation of Data Manipultation Language, It is used to insert, delete, update the Data which is stored in database

Examples : SELECT, UPDATE, INSERT statements

INSERT into Employee(name,age) values('Rajesh',23)

SELECT id,name From Employee

Update Employee
set        name = 'Rajesh Kumar',
            age    = '24'
Where id =1

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DCL

DCL is the abbreviation of Data Control Language , It is used to create roles, Permission

Examples : GRANT, REVOKE

Grant exec on stored_procedure to public

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TCL

TCL is the abbreviation of Transactional Control Language,It is used to manage the transactions takes place in database.

Example COMMIT, ROLLBACK


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