Returning modified rows with RETURNING in PostgreSQL

Introduction

The RETURNING clause lets you see the rows that were changed by an INSERT, UPDATE, or DELETE right away. This helps you confirm what happened without running another query.

After adding new data, to get the new row's ID or details immediately.

When updating records, to check which rows changed and what their new values are.

When deleting rows, to know exactly which rows were removed.

When you want to avoid extra queries to fetch updated or inserted data.

When you need to log or audit changes made by your query.

Syntax

PostgreSQL

INSERT INTO table_name (column1, column2) VALUES (value1, value2) RETURNING *;

UPDATE table_name SET column1 = value1 WHERE condition RETURNING *;

DELETE FROM table_name WHERE condition RETURNING *;

The RETURNING clause goes at the end of your INSERT, UPDATE, or DELETE statement.

Using RETURNING * returns all columns of the affected rows, but you can specify specific columns instead.

Examples

Insert a new employee and get back their ID and name immediately.

PostgreSQL

INSERT INTO employees (name, role) VALUES ('Alice', 'Engineer') RETURNING id, name;

Update Alice's role and return all her updated information.

PostgreSQL

UPDATE employees SET role = 'Senior Engineer' WHERE name = 'Alice' RETURNING *;

Delete Alice's record and return her ID and name to confirm deletion.

PostgreSQL

DELETE FROM employees WHERE name = 'Alice' RETURNING id, name;

Sample Program

This example creates a temporary employees table, inserts a row, updates it, and then deletes it. Each step returns the affected rows so you can see the changes immediately.

PostgreSQL

CREATE TEMP TABLE employees (id SERIAL PRIMARY KEY, name TEXT, role TEXT);

INSERT INTO employees (name, role) VALUES ('Bob', 'Developer') RETURNING id, name, role;

UPDATE employees SET role = 'Lead Developer' WHERE name = 'Bob' RETURNING *;

DELETE FROM employees WHERE name = 'Bob' RETURNING id, name;

Important Notes

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

Using RETURNING can save time and reduce errors by avoiding extra SELECT queries.

Summary

RETURNING shows you the rows changed by INSERT, UPDATE, or DELETE immediately.

You can return all columns with RETURNING * or select specific columns.

This helps confirm changes and avoid extra queries.

Practice

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

easy

A. It delays the update until a commit is issued.

B. It prevents the update from modifying any rows.

C. It returns the rows that were updated immediately after the update.

D. It returns the number of rows in the table before the update.

Solution

1. Step 1: Understand the purpose of RETURNING

   The RETURNING clause is used to get the data of rows affected by an INSERT, UPDATE, or DELETE immediately.

2. Step 2: Apply to UPDATE statement

   When used with UPDATE, RETURNING shows the updated rows without needing a separate SELECT query.

3. Final Answer:

   It returns the rows that were updated immediately after the update. -> Option C

4. Quick Check:

   RETURNING shows changed rows = B [OK]

Hint: RETURNING shows changed rows right after modification [OK]

Common Mistakes:

• Thinking RETURNING delays changes
• Assuming RETURNING prevents updates
• Confusing RETURNING with row count only

2. Which of the following is the correct syntax to return all columns of updated rows in PostgreSQL?

easy

A. UPDATE table_name SET col = val RETURNING ALL COLUMNS;

B. UPDATE table_name SET col = val RETURNING *;

C. UPDATE table_name SET col = val RETURNING ALL;

D. UPDATE table_name SET col = val RETURN *;

Solution

1. Step 1: Recall correct RETURNING syntax

   PostgreSQL uses RETURNING followed by column names or * to return all columns.

2. Step 2: Identify correct option

   Only UPDATE table_name SET col = val RETURNING *; uses RETURNING * which is valid syntax to return all columns.

3. Final Answer:

   UPDATE table_name SET col = val RETURNING *; -> Option B

4. Quick Check:

   RETURNING * returns all columns [OK]

Hint: Use RETURNING * to get all columns after update [OK]

Common Mistakes:

• Using RETURN instead of RETURNING
• Writing RETURNING ALL instead of RETURNING *
• Adding extra keywords like ALL COLUMNS

3. Given the table users(id INT, name TEXT, age INT) with rows:
(1, 'Alice', 30), (2, 'Bob', 25)
What will this query return?

UPDATE users SET age = age + 1 WHERE id = 2 RETURNING id, age;

medium

A. (2, 26)

B. (2, 25)

C. (1, 31)

D. (1, 30)

Solution

1. Step 1: Identify updated row

   The WHERE clause updates only the row with id = 2 (Bob).

2. Step 2: Calculate new age and returned columns

   Bob's age increases from 25 to 26. RETURNING id, age returns (2, 26).

3. Final Answer:

   (2, 26) -> Option A

4. Quick Check:

   Updated row with id=2 returns new age 26 [OK]

Hint: RETURNING shows updated values immediately [OK]

Common Mistakes:

• Returning old values instead of updated
• Confusing which row is updated
• Ignoring WHERE clause effect

4. What is wrong with this query?

UPDATE products SET price = price * 1.1 RETURNING;

medium

A. RETURNING cannot be used with UPDATE statements.

B. The multiplication operator * is invalid in UPDATE.

C. Missing WHERE clause causes syntax error.

D. RETURNING clause requires columns or * to specify what to return.

Solution

1. Step 1: Check RETURNING syntax

   RETURNING must be followed by column names or *; empty RETURNING is invalid syntax.

2. Step 2: Validate other parts

   Multiplication and UPDATE without WHERE are valid; RETURNING with no columns is the error.

3. Final Answer:

   RETURNING clause requires columns or * to specify what to return. -> Option D

4. Quick Check:

   RETURNING needs columns or * [OK]

Hint: Always specify columns or * after RETURNING [OK]

Common Mistakes:

• Leaving RETURNING empty
• Thinking WHERE is mandatory for syntax
• Believing RETURNING disallowed in UPDATE

5. You want to increase the salary by 10% for employees in department 5 and get their id and new salary. Which query correctly does this and returns the updated rows?

hard

A. UPDATE employees SET salary = salary * 1.1 WHERE department_id = 5 RETURNING id, salary;

B. UPDATE employees SET salary = salary + 10 WHERE department_id = 5 RETURNING *;

C. UPDATE employees SET salary = salary * 1.1 RETURNING id, salary WHERE department_id = 5;

D. UPDATE employees SET salary = salary * 1.1 WHERE department_id = 5 RETURN id, salary;

Solution

1. Step 1: Identify correct UPDATE with WHERE and RETURNING

   The query must update only department 5 employees and return id and salary.

2. Step 2: Check syntax correctness

   UPDATE employees SET salary = salary * 1.1 WHERE department_id = 5 RETURNING id, salary; uses correct syntax: UPDATE ... SET ... WHERE ... RETURNING id, salary;

3. Step 3: Eliminate incorrect options

   Adding a fixed 10 instead of multiplying by 1.1 doesn't implement a 10% increase. Placing RETURNING before WHERE is invalid syntax. Using RETURN instead of RETURNING is wrong.

4. Final Answer:

   UPDATE employees SET salary = salary * 1.1 WHERE department_id = 5 RETURNING id, salary; -> Option A

5. Quick Check:

   Correct syntax with WHERE and RETURNING columns [OK]

Hint: RETURNING follows WHERE clause with columns listed [OK]

Common Mistakes:

• Placing RETURNING before WHERE
• Using RETURN instead of RETURNING
• Adding fixed amount instead of percentage