If you’re getting an error that reads “The function ‘ROW_NUMBER’ must have an OVER clause with ORDER BY” in SQL Server, it’s probably because you’re calling the ROW_NUMBER() function without an ORDER BY clause.

Window functions such as ROW_NUMBER() require an OVER clause, and that clause must have an ORDER BY clause. If you’re getting the above error, there’s a good chance you’re providing an OVER clause, but you’re omitting the ORDER BY clause.

To fix this issue, add an ORDER BY clause to the OVER clause when calling the ROW_NUMBER() function.

Example of Error

Here’s an example of code that produces the error:

SELECT
    ROW_NUMBER( ) OVER ( 
        PARTITION BY VendorId
        ) AS ROW_NUMBER,
    VendorId,
    ProductName,
    ProductPrice
FROM Products;

Result:

Msg 4112, Level 15, State 1, Line 2
The function 'ROW_NUMBER' must have an OVER clause with ORDER BY.

This error occurred because I called the ROW_NUMBER() function without an ORDER BY clause.

More specifically, it happened because I didn’t put an ORDER BY clause in the OVER clause.

Solution

To fix this issue, add an ORDER BY clause to the OVER clause:

SELECT
    ROW_NUMBER( ) OVER ( 
        PARTITION BY VendorId
        ORDER BY ProductPrice
        ) AS ROW_NUMBER,
    VendorId,
    ProductName,
    ProductPrice
FROM Products;

Result:

ROW_NUMBER  VendorId  ProductName                      ProductPrice
----------  --------  -------------------------------  ------------
1           1001      Long Weight (green)              11.99       
2           1001      Long Weight (blue)               14.75       
3           1001      Left handed screwdriver          25.99       
4           1001      Right handed screwdriver         25.99       
1           1002      Sledge Hammer                    33.49       
1           1003      Hammock                          10          
2           1003      Straw Dog Box                    55.99       
3           1003      Chainsaw                         245         
1           1004      Bottomless Coffee Mugs (4 Pack)  9.99        
2           1004      Tea Pot                          12.45       

This time the function worked as expected.

In this example I also used the PARTITION BY clause to partition the result set, but this is optional. We can omit the PARTITION BY clause but we can’t omit the ORDER BY clause.