SQL Commands

Common SQL commands for querying and managing relational databases.

Action	Command	Details
Select all	`SELECT * FROM table;`	Retrieve all records from a table.
Select specific columns	`SELECT column1, column2 FROM table;`	Retrieve specified columns from a table.
Where clause	`SELECT * FROM table WHERE condition;`	Filter rows that satisfy a condition.
Insert row	`INSERT INTO table (col1, col2) VALUES (val1, val2);`	Add a new row to a table.
Update row	`UPDATE table SET col = val WHERE condition;`	Modify existing records.
Delete row	`DELETE FROM table WHERE condition;`	Remove records matching condition.
Create table	`CREATE TABLE table_name (id INT PRIMARY KEY, col VARCHAR(100));`	Define a new table.
Drop table	`DROP TABLE table_name;`	Delete a table and all its data.
Join tables	`SELECT * FROM a JOIN b ON a.id = b.a_id;`	Combine rows from two tables based on related columns.
Group by	`SELECT col, COUNT(*) FROM table GROUP BY col;`	Aggregate rows by column.
Order by	`SELECT * FROM table ORDER BY col DESC;`	Sort query results.
Limit results	`SELECT * FROM table LIMIT 10;`	Return limited number of rows.
Create index	`CREATE INDEX idx_name ON table (col);`	Improve query performance.
Alter table add column	`ALTER TABLE table ADD col INT;`	Add a new column.
Transaction start	`BEGIN TRANSACTION;`	Start a database transaction.
Transaction commit	`COMMIT;`	Save all changes made in the transaction.
Transaction rollback	`ROLLBACK;`	Undo all changes in the transaction.