Why Does PostgreSQL Throw Error 42601: 'a column definition list is required for functions returning 'record''?

ERROR: 42601: a column definition list is required for functions returning "record"

The provided error: "ERROR: 42601: a column definition list is required for functions returning "record"" commonly occurs when creating a PostgreSQL function that attempts to return a record without explicitly defining the column structure.

Returns Table

To resolve this error, use the RETURNS TABLE syntax to specify the structure of the data being returned by the function. Here's an example:

CREATE OR REPLACE FUNCTION get_user_by_username(
    username VARCHAR(250),
    online BOOLEAN
) RETURNS TABLE (
    user_id INTEGER,
    user_name VARCHAR(250),
    last_activity TIMESTAMP
) 
AS $$
...

In this example, the get_user_by_username function returns a table with three columns: user_id, user_name, and last_activity.

Returns Specific Columns

Alternatively, you can specify the specific columns returned by the function using RETURNS SETOF as follows:

CREATE OR REPLACE FUNCTION get_user_by_username(
    username VARCHAR(250),
    online BOOLEAN
) RETURNS SETOF (
    user_id INTEGER,
    user_name VARCHAR(250),
    last_activity TIMESTAMP
) 
AS $$
...

Other Considerations

Here are a few additional considerations to keep in mind:

• Ensure that your function has a LANGUAGE statement specifying the language it uses (e.g., LANGUAGE plpgsql).
• Define any custom types or variables used within the function.
• Verify that the function's logic correctly handles both the online and offline scenarios.
• Consider using RETURNING within your UPDATE statement to directly return the updated record.
• Avoid unnecessary loops or complex logic within the function.

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