Database Languages

A database language is used to define, access, manipulate, and control data in a DBMS. Four categories — remember DDL · DML · DCL · TCL.

DDL — Data Definition Language

Defines and changes the structure (schema) of database objects (tables, views, indexes).

Commands: CREATE, ALTER, DROP, TRUNCATE, RENAME.

CREATE TABLE Student (
  student_id INT PRIMARY KEY,
  name VARCHAR(50),
  dept VARCHAR(30)
);

ALTER TABLE Student ADD email VARCHAR(60);

DML — Data Manipulation Language

Works with the data (rows) inside tables — insert, update, delete, query.

Commands: SELECT, INSERT, UPDATE, DELETE.

INSERT INTO Student(student_id, name, dept)
VALUES (1, 'Rahim', 'CSE');

UPDATE Student SET dept = 'EEE' WHERE student_id = 1;

SELECT * FROM Student;

DCL — Data Control Language

Controls access / permissions (security) on database objects.

Commands: GRANT, REVOKE.

GRANT SELECT, INSERT ON Student TO user1;
REVOKE INSERT ON Student FROM user1;

TCL — Transaction Control Language

Manages transactions to ensure consistency (commit, rollback, savepoints).

Commands: COMMIT, ROLLBACK, SAVEPOINT, SET TRANSACTION.

SAVEPOINT sp1;
UPDATE Student SET dept = 'CE' WHERE student_id = 1;
ROLLBACK TO sp1;   -- undo after savepoint
COMMIT;            -- permanently save

One-line summary

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