How to diagnose and fix the 22016 invalid_argument_for_nth_value_function error code in Postgres.

by

The 22016 error code in PostgreSQL, described as invalid_argument_for_nth_value_function, occurs when an invalid argument or incorrect number of arguments is passed to the NTH_VALUE() window function, which is used to return the value of the specified expression from the N-th row of the window frame.

To diagnose and fix an invalid_argument_for_nth_value_function error, you should:

  1. Review the NTH_VALUE() Usage: Ensure that you are using the NTH_VALUE() function correctly, with the expression to be evaluated and the row number as its arguments.
  2. Check the Arguments: The second argument to NTH_VALUE() must be a positive integer literal, specifying the N-th row from which to retrieve the value.
  3. Examine the Window Frame: The window frame (specified by the ROWS or RANGE clause) should be set such that the N-th row is actually within the frame.

Here are some examples to illustrate how you might fix an invalid_argument_for_nth_value_function:

Example 1: Incorrect Number of Arguments

SELECT NTH_VALUE(salary, 1, 2) OVER (ORDER BY hire_date)
FROM employees;

The above query will raise an invalid_argument_for_nth_value_function because NTH_VALUE() expects exactly two arguments. To fix this, remove the extra argument:

SELECT NTH_VALUE(salary, 1) OVER (ORDER BY hire_date)
FROM employees;

Example 2: Non-positive Integer as Second Argument

SELECT NTH_VALUE(salary, -1) OVER (ORDER BY hire_date)
FROM employees;

This will raise an invalid_argument_for_nth_value_function because the second argument must be a positive integer. To fix this, provide a positive integer:

SELECT NTH_VALUE(salary, 1) OVER (ORDER BY hire_date)
FROM employees;

Example 3: N-th Row Outside the Window Frame

SELECT NTH_VALUE(salary, 5) OVER (
    ORDER BY hire_date
    ROWS BETWEEN CURRENT ROW AND 3 FOLLOWING
) FROM employees;

This may raise an invalid_argument_for_nth_value_function if the 5th row is outside the specified window frame. To fix this, adjust the window frame to include the 5th row:

SELECT NTH_VALUE(salary, 5) OVER (
    ORDER BY hire_date
    ROWS BETWEEN CURRENT ROW AND 4 FOLLOWING
) FROM employees;

Make sure to test your query after making these adjustments to verify that the error has been resolved. For more detailed information on PostgreSQL error codes, you can refer to the PostgreSQL Error Codes documentation, and for the NTH_VALUE() function, you can review the PostgreSQL documentation on window functions.

Leave a Comment