Functions returning TABLE in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does a PostgreSQL function returning TABLE do?

It returns a set of rows with defined columns, like a table, allowing you to get multiple rows and columns from a single function call.

beginner

How do you define the columns returned by a function returning TABLE in PostgreSQL?

You specify the column names and their data types in the RETURNS TABLE clause of the function definition.

intermediate

What SQL statement inside a function returning TABLE provides the rows to return?

A RETURN QUERY statement is used to return the rows from a SELECT or other query inside the function.

intermediate

Can a function returning TABLE be used in a FROM clause like a regular table?

Yes, you can call the function in the FROM clause and treat its output like a table to join or filter results.

advanced

What is the benefit of using functions returning TABLE over returning SETOF RECORD?

Functions returning TABLE have named columns and types defined upfront, making them easier to use and safer because the output structure is fixed.

Which keyword defines the columns and types a PostgreSQL function will return as a table?

A RETURNS TABLE

B RETURNS SETOF

C RETURNS RECORD

D RETURNS ROW

RETURNS TABLE specifies the column names and types the function will return as a table.

Inside a function returning TABLE, which statement returns the query result rows?

A RETURN ROW

B RETURN NEXT

C RETURN SET

D RETURN QUERY

RETURN QUERY returns the result of a query as the function output rows.

How can you use a function returning TABLE in a SQL query?

A In the FROM clause like a table

B Only in the WHERE clause

C Only in the SELECT list

D Only in the ORDER BY clause

Functions returning TABLE can be called in the FROM clause and treated like tables.

What is a key advantage of RETURNS TABLE over RETURNS SETOF RECORD?

A RETURNS TABLE is faster to execute

B RETURNS TABLE defines output columns explicitly

C RETURNS TABLE can return scalar values only

D RETURNS TABLE does not support multiple rows

RETURNS TABLE explicitly defines output columns and types, making usage clearer and safer.

Which of these is a valid way to define a function returning TABLE in PostgreSQL?

A CREATE FUNCTION get_users() RETURNS VOID AS $$ BEGIN END; $$ LANGUAGE plpgsql;

B CREATE FUNCTION get_users() RETURNS INT AS $$ SELECT id FROM users; $$ LANGUAGE sql;

C CREATE FUNCTION get_users() RETURNS TABLE(id INT, name TEXT) AS $$ BEGIN RETURN QUERY SELECT id, name FROM users; END; $$ LANGUAGE plpgsql;

D CREATE FUNCTION get_users() RETURNS RECORD AS $$ SELECT id, name FROM users; $$ LANGUAGE sql;

Option C correctly defines a function returning TABLE with columns and uses RETURN QUERY.

Explain how to create a PostgreSQL function that returns multiple rows and columns using RETURNS TABLE.

Think about how to define output columns and how to return query results inside the function.

Describe the difference between RETURNS TABLE and RETURNS SETOF RECORD in PostgreSQL functions.

Consider how output structure is handled in both cases.