Lesson 8.4

Deleting Rows Safely with SQL DELETE

DELETE removes rows from a table. Preview the target rows first, and use a transaction when you need a rollback path.

DELETE removes rows, and like UPDATE it obeys your WHERE clause, or deletes everything if you forget it.

The safe ritual is two steps: first SELECT the rows your filter matches and eyeball them, then run the same filter as a DELETE. The starter below is that first step. Run it before you change anything.

Pattern

-- 1. measure
select * from orders where status = 'cancelled';

-- 2. cut
delete from orders where status = 'cancelled';

Syntax reference

Need syntax details? See the safe UPDATE and DELETE reference

Schema · Garden Shop Table · orders 6 columns · 24 rows

Table · orders

One row per order. Unshipped orders have a null shipped_date.

6 columns · 24 rows

order_id int customer_id int order_date date shipped_date date status text coupon_code text

Your task

The shop purges cancelled orders. First run the starter to see which orders are 'cancelled'. Then delete every order with that status. Confirm the purge touched only those orders: return each status with its count(*) as orders, sorted by status.

Garden Shop · SQL engine loading · Ctrl/⌘ + Enter to run·

Run your query to inspect the result.

Expected answer

Columns: status, orders.
Rows: 3 statuses, sorted by status. cancelled no longer appears.
pending 3, processing 3, shipped 17: 23 orders, one fewer than before. A DELETE with no WHERE returns no rows at all.

Previous · 8.3 Changing rows with UPDATE

Next · 8.5 Transactions and ROLLBACK →

Reference

Safe SQL UPDATE and DELETE

A checklist for changing the right rows.

Lesson

What Is SQL DML?

Understand INSERT, UPDATE, and DELETE.

Lesson

Adding Rows with SQL INSERT

Add rows and confirm they landed.

Lesson