Four Common SQL Commands
SQL commands help control what happens inside a database. The four examples below show how to retrieve, add, change, and remove records.
SELECT
The SELECT command retrieves records from a table.
SELECT * FROM customers;
INSERT
The INSERT command adds a new record to a table.
INSERT INTO customers (customer_id, first_name, last_name, city) VALUES (1, 'Sam', 'Johnson', 'Chicago');
UPDATE
The UPDATE command changes information already stored in a table.
UPDATE customers SET city = 'Naperville' WHERE customer_id = 1;
DELETE
The DELETE command removes a record from a table.
DELETE FROM customers WHERE customer_id = 1;
How SQL Supports Real Websites
| Website Feature | Database Action | SQL Example |
|---|---|---|
| User login | Checks a user record | SELECT |
| New account | Adds a user record | INSERT |
| Profile edit | Changes saved information | UPDATE |
| Account removal | Deletes selected information | DELETE |