SQL Commands 

Data Definition Language (DDL)

1. CREATE – Creates a new table, database, index, or view.

   CREATE TABLE Employees (
       ID INT PRIMARY KEY,
       Name VARCHAR(50),
       Age INT,
       Department VARCHAR(50)
   );
   

2. ALTER – Modifies an existing database structure.

   ALTER TABLE Employees ADD Salary DECIMAL(10,2);
   

3. DROP – Deletes a database object (table, database, etc.).

   DROP TABLE Employees;
   

4. TRUNCATE – Removes all records from a table but keeps its structure.

   TRUNCATE TABLE Employees;
   

Data Manipulation Language (DML)

• INSERT – Adds new rows to a table.

  INSERT INTO Employees (ID, Name, Age, Department) VALUES (1, 'John Doe', 30, 'HR');
  

• UPDATE – Modifies existing records.

  UPDATE Employees SET Age = 31 WHERE ID = 1;
  

• DELETE – Removes records from a table.

  DELETE FROM Employees WHERE ID = 1;
  

Data Query Language (DQL)

• SELECT – Retrieves data from a database.

  SELECT * FROM Employees;

Data Control Language (DCL)

• GRANT – Provides access to users.

  GRANT SELECT, INSERT ON Employees TO user_name;
  

• REVOKE – Removes user access.

  REVOKE INSERT ON Employees FROM user_name;
  

Transaction Control Language (TCL)

• COMMIT – Saves changes permanently.

  COMMIT;
  

• ROLLBACK – Reverts uncommitted changes.

  ROLLBACK;

• SAVEPOINT – Creates a savepoint in a transaction.

           SAVEPOINT Save1;