DML, DCL and TCL commands in SQL database.pptx
- 1. DQL commands It consists of only 1 command i.e. SELECT command. SELECT it is used to retrieve all the records or particular record from table. Syntax : i. SELECT * from <table_name>; This will retrieve all the records from table. ii. SELECT * from <table_name> WHERE condition; This will retrieve particular records from table, according to specified condition. Mrs. Pallavi Patil
- 2. DML commands 1. Insert command Used to insert values into created table. Syntax 1: for inserting single row Insert into <table_name> values(value1, value2,…..,value n); Ex. Insert into student values(111,’aaa’,86); Syntax 2 : by using attribute list Insert into <table_name> (attribute1, attribute2,…….,attribute n) values (value1, value2,……., value n); Mrs. Pallavi Patil
- 3. Syntax 3: for inserting values for particular column Insert into <table_name>(column1, column2)values(value1, value2); 2. Update command It is used to change data values in the table. We can update one or more values using update command. Syntax: UPDATE <table_name> SET column_name=expression WHERE condition; Ex. UPDATE student SET marks= marks+3 where class =‘TY’; Mrs. Pallavi Patil
- 4. 3. DELETE This command is used to delete particular rows or records from the database table. DELETE command without WHERE clause will delete all the records from table. • syntax 1: DELETE from <table_name> WHERE condition; This syntax is used to delete particular record. • Syntax 2: DELETE from <Table_name>; This syntax will delete all the records from table. Mrs. Pallavi Patil
- 5. DCL commands • Used to control various user actions like insert, update, delete or viewing data. • DCL commands also perform task of assigning privileges. So user can access certain objects in database. Mrs. Pallavi Patil
- 6. Create user • The database administrator can create users of database by using this command. Syntax: Create user <username> identified by <password>; Ex. Create user admin1 identified by ad123; GRANT • Grant command allows user to do certain operations on other user’s table. • The different types of previleges can be granted to users such as alter, insert, delete, update, select, etc. Mrs. Pallavi Patil
- 7. Syntax: Grant <privilege list> on <TableName> to <username>; Ex. Grant insert , update on student_info to admin1; REVOKE • It is used to cancel or to take back the granted privileges from the specific user. Syntax Revoke <privileges list> on table_name from <user_name>; Ex. Revoke insert on student_info from admin1; Mrs. Pallavi Patil
- 8. TCL Commands COMMIT command • It is used to make changes permanent in the database. This command is used to end the transaction. Syntax: COMMIT; Mrs. Pallavi Patil
- 9. Savepoint • Savepoints are treated as marker to divide very lengthy transactions into smaller one. • We can create marker within current transaction using savepoint statement. • All savepoints get erased when commit command is used. • You can rollback the transactions after certain savepoint without rolling back entire transaction. Syntax: Savepoint savepoint_name; Mrs. Pallavi Patil
- 10. Savepoint sp1; DELETE from student where rollno=3; Savepoint sp2; Update student set student_name=‘ABC’ where rollno=1; Delete from student where rollno=5; Savepoint sp3; Delete from student where rollno=8; Mrs. Pallavi Patil
- 11. 3. Rollback • Rollback is used to undo or cancel the changes done in current transactions. • We rollback entire transactions using rollback command or if savepoint is given, rollback can be done till specific savepoint. Syntax: Rollback; Or Rollback to savepoint_name; Mrs. Pallavi Patil