DELETE with RETURNING clause in PostgreSQL

Introduction

The DELETE statement removes rows from a table. The RETURNING clause lets you see which rows were deleted right away.

You want to delete old records but also keep a copy of what was removed.

You need to delete a user but want to log their details immediately.

You want to remove expired sessions and see their IDs for cleanup.

You want to delete orders but return the order numbers for confirmation.

Syntax

PostgreSQL

DELETE FROM table_name
WHERE condition
RETURNING column1, column2, ...;

The RETURNING clause lists columns to show from deleted rows.

If you want all columns, use RETURNING *.

Examples

Deletes the employee with id 5 and returns their name and department.

PostgreSQL

DELETE FROM employees
WHERE id = 5
RETURNING name, department;

Deletes all expired sessions and returns all columns of those deleted rows.

PostgreSQL

DELETE FROM sessions
WHERE expired = true
RETURNING *;

Sample Program

This example creates a temporary users table, inserts three users, then deletes the inactive ones. It returns the id and name of deleted users.

PostgreSQL

CREATE TEMP TABLE users (id SERIAL PRIMARY KEY, name TEXT, active BOOLEAN);

INSERT INTO users (name, active) VALUES
('Alice', true),
('Bob', false),
('Carol', false);

DELETE FROM users
WHERE active = false
RETURNING id, name;

Important Notes

RETURNING is specific to PostgreSQL and some other databases; not all support it.

It helps avoid running a separate SELECT after DELETE to know what was removed.

Summary

DELETE removes rows from a table based on a condition.

RETURNING shows which rows were deleted immediately.

Use RETURNING * to get all columns of deleted rows.

Practice

1. What does the RETURNING clause do in a DELETE statement in PostgreSQL?

easy

A. It counts the number of rows in the table.

B. It prevents rows from being deleted.

C. It updates rows instead of deleting them.

D. It returns the rows that were deleted.

Solution

1. Step 1: Understand DELETE operation

   The DELETE statement removes rows from a table based on a condition.

2. Step 2: Role of RETURNING clause

   The RETURNING clause outputs the rows that were deleted, showing their data immediately.

3. Final Answer:

   It returns the rows that were deleted. -> Option D

4. Quick Check:

   RETURNING shows deleted rows [OK]

Hint: RETURNING shows deleted rows immediately [OK]

Common Mistakes:

• Thinking RETURNING prevents deletion
• Confusing RETURNING with UPDATE
• Assuming RETURNING counts rows

2. Which of the following is the correct syntax to delete rows from users where age < 18 and return all deleted rows?

easy

A. DELETE FROM users WHERE age < 18 RETURNING *;

B. DELETE users WHERE age < 18 RETURNING *;

C. DELETE FROM users RETURNING * WHERE age < 18;

D. DELETE FROM users WHERE age < 18 RETURNING all;

Solution

1. Step 1: Check DELETE syntax

   The correct DELETE syntax is: DELETE FROM table WHERE condition.

2. Step 2: Use RETURNING clause correctly

   RETURNING * must come after WHERE clause to return all columns of deleted rows.

3. Final Answer:

   DELETE FROM users WHERE age < 18 RETURNING *; -> Option A

4. Quick Check:

   Correct DELETE syntax with RETURNING * [OK]

Hint: DELETE FROM ... WHERE ... RETURNING *; is correct syntax [OK]

Common Mistakes:

• Omitting FROM keyword
• Placing RETURNING before WHERE
• Using RETURNING all instead of *

3. Given the table products with rows:
{id:1, name:'Pen', stock:10}, {id:2, name:'Pencil', stock:0}, {id:3, name:'Eraser', stock:5}
What will this query return?

DELETE FROM products WHERE stock = 0 RETURNING id, name;

medium

A. [{id:1, name:'Pen'}, {id:3, name:'Eraser'}]

B. []

C. [{id:2, name:'Pencil'}]

D. Syntax error

Solution

1. Step 1: Identify rows matching condition

   Only the product with stock = 0 is {id:2, name:'Pencil'}.

2. Step 2: DELETE removes matching rows and RETURNING outputs specified columns

   The query deletes that row and returns its id and name.

3. Final Answer:

   [{id:2, name:'Pencil'}] -> Option C

4. Quick Check:

   Deleted rows with stock=0 returned [OK]

Hint: RETURNING shows deleted rows matching WHERE [OK]

Common Mistakes:

• Returning all rows instead of matching ones
• Expecting deleted rows to remain in table
• Confusing syntax causing errors

4. What is wrong with this query?

DELETE FROM orders RETURNING * WHERE status = 'cancelled';

medium

A. The WHERE clause must come before RETURNING.

B. RETURNING * is not allowed in DELETE.

C. Missing semicolon at the end.

D. DELETE cannot filter rows.

Solution

1. Step 1: Check clause order in DELETE

   In PostgreSQL, WHERE clause must come before RETURNING clause.

2. Step 2: Identify error in query

   The query places RETURNING * before WHERE, which is invalid syntax.

3. Final Answer:

   The WHERE clause must come before RETURNING. -> Option A

4. Quick Check:

   WHERE before RETURNING in DELETE [OK]

Hint: WHERE clause always before RETURNING [OK]

Common Mistakes:

• Placing RETURNING before WHERE
• Thinking RETURNING is disallowed
• Ignoring clause order rules

5. You want to delete all employees from staff who have salary < 30000 and return their id and name. Which query correctly does this and also returns the count of deleted rows?

hard

A. DELETE FROM staff WHERE salary < 30000 RETURNING id, name, COUNT(*);

B. WITH deleted AS (DELETE FROM staff WHERE salary < 30000 RETURNING id, name) SELECT COUNT(*) FROM deleted;

C. DELETE FROM staff RETURNING id, name WHERE salary < 30000; SELECT COUNT(*) FROM staff;

D. DELETE FROM staff WHERE salary < 30000; SELECT id, name FROM staff RETURNING COUNT(*);

Solution

1. Step 1: Delete rows with condition and return columns

   Using DELETE ... WHERE salary < 30000 RETURNING id, name returns deleted rows.

2. Step 2: Use WITH clause to capture deleted rows and count them

   WITH deleted AS (...) lets us select COUNT(*) from deleted rows in one query.

3. Final Answer:

   WITH deleted AS (DELETE FROM staff WHERE salary < 30000 RETURNING id, name) SELECT COUNT(*) FROM deleted; -> Option B

4. Quick Check:

   Use WITH + RETURNING to delete and count [OK]

Hint: Use WITH clause to count deleted rows with RETURNING [OK]

Common Mistakes:

• Trying to use COUNT(*) inside RETURNING
• Placing WHERE after RETURNING
• Separating DELETE and count without capturing deleted rows