SQL Commands
Duration : 00:02:00
Data Definition Language (DDL)
DDL is used for defining and managing the structure of a database, including creating, altering, and deleting database objects such as tables, indexes, and views.CREATE
Used to create database objects like tables, views, and indexes.Example
CREATE TABLE employees (
emp_id INT PRIMARY KEY,
emp_name VARCHAR(50)
);
DROP
Used to delete database objects like tables or views.Example
DROP TABLE employees;
ALTER
Used to modify the structure of existing database objects.Example
ALTER TABLE employees
ADD emp_salary DECIMAL(10, 2);
Data Manipulation Language (DML)
DML is used for manipulating the data stored within a database, including inserting, updating, and deleting records within tables.INSERT
Used to insert data into a table.Example
INSERT INTO employees (emp_id, emp_name, emp_salary)
VALUES (1, 'John Doe', 50000);
UPDATE
Used to modify existing data in a table.Example
UPDATE employees
SET emp_salary = 55000
WHERE emp_id = 1;
DELETE
Used to remove data from a table.Example
DELETE FROM employees
WHERE emp_id = 1;
Data Control Language (DCL)
DCL is used for managing the permissions and access control to the database objects, including granting and revoking privileges to users and roles. GRANT: Used to give specific privileges to users or roles.Example
GRANT SELECT ON employees TO user1;
REVOKE
Used to revoke previously granted privileges from users or roles.Example
REVOKE SELECT ON employees FROM user1;
Transaction Control Language (TCL)
TCL is used for managing transactions within a database, including controlling their initiation, committing changes, and rolling back in case of errors. COMMIT: Used to save changes made during the current transaction.Example
COMMIT;
ROLLBACK
Used to undo changes made during the current transaction.Example
ROLLBACK;
SAVEPOINT
Used to set a point within a transaction to which you can later roll back.Example
SAVEPOINT my_savepoint;
Data Query Language (DQL)
DQL is used for querying and retrieving data from the database using SQL SELECT statements.SELECT
Used to retrieve data from one or more tables.Example
SELECT emp_name, emp_salary
FROM employees
WHERE emp_salary > 50000;
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