Data Definition (DDL)
Create a new table
CREATE TABLE users ( id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(100) NOT NULL );
Drop a table
DROP TABLE users;
Add a column
ALTER TABLE users ADD email VARCHAR(255) DEFAULT NULL;
Rename a table
ALTER TABLE users
RENAME TO members;
Data Manipulation (DML)
Select rows
SELECT id, name
FROM users
WHERE status = 'active';
Insert a row
INSERT INTO users (name, email)
VALUES ('Alice', 'alice@example.com');
Update rows
UPDATE users
SET status = 'inactive'
WHERE last_login < '2025-01-01';
Delete rows
DELETE FROM users
WHERE status = 'inactive';
Transactions
Start a transaction
BEGIN TRANSACTION;
Commit changes
COMMIT;
Roll back changes
ROLLBACK;
Index Management
Create an index
CREATE INDEX idx_users_email
ON users (email);
Drop an index
DROP INDEX idx_users_email
ON users;
Permissions
Grant privileges
GRANT SELECT, INSERT
ON shop.*
TO 'webuser'@'localhost';
Revoke privileges
REVOKE INSERT
ON shop.*
FROM 'webuser'@'localhost';