Basics of Database Part 3

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SQL Command Groups 


DDL( Data Definition Language): Creation of Objects


DML( Data Manipulation Language): Manipulation of data


DCL( Data Control Language): Assignment & removal of permissions


TCL( Transaction Control Language): Saving and restoring changes to a database.


DDL( Data Definition Language)


Create: Creates object in the database/database objects.


Alter: Alters the structure of the database/database objects


Drop: Delete Objects from the database


Truncate: Remove all records from the table permanently


Rename: Rename an object.


Syntax: create table table name(

             column name data type,

             column n data type,

              primary key (one or more columns)


              );


Exp: create table emp(

                      emp_id int(10) not null,

                      first_name varchar(20),

                      last_name varchar (20) not null,

                      salary int (10) not null,

                     primary key (emp_id)

                                       );


How to see the created table?


Syntax: select * from table name;


Exp: select * from emp;


How to see the logic of created table?


Syntax: describe table name;


Exp: describe emp;


How to add a new column in a table?


Syntax: alter table table name add column column name data type;


Exp: alter table emp add column contact int(10);


How to rename a column in a table?


Syntax: alter table table name rename column column name to new column name;


Exp: alter table emp rename column contact to job_code;


How to delete records from table?


Syntax: truncate table table name;


Exp: truncate table emp;


How to delete a table?


Syntax: drop table table name;


Exp: drop table emp;


DML( Data Manipulation Language)


How to insert data into the table?


Syntax: insert into table name ( column 1, column 2, ..... column n) 

              values 

              (values 1, values 2, ......., values n);


Exp: insert into emp (emp_id, first_name, last_name, salary)

        values

        (101, 'Robin', 'Sharma' , 100000);


How we can update something in the table?


Syntax: update table name set column 1 = value 1

               where [condition];


Exp: update emp set last_name='Cholen' where emp_id=101;


If we need to delete something


Syntax: delete from table name where column name where (condition);


Exp: delete from emp where emp_id = 101;


DCL: Data Control Language)


Grant: Give access privileges to the database.


Syntax: grant <privilege list> on <relation name> to <user>


Revoke: Withdraws access privileges given with the grant command.


Syntax: revoke <privilege list> on <relation name> to <user>


TCL(Transaction Control Language)


Commit: Saves the work done.


Rollback: Restore the database to the origin state since the last commit.


Savepoint: Identify a point in a transaction to which you can roll back later.


#work #sql #day3 #database #language 


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Contact no: 8127430702

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