RowNumber() Over(Order By x) with a subquery not working

Question

The 'count' query runs fine. The 'Page of records' query runs fine as long as the commented section stays as-is. If uncommented it never returns... just keeps going. Any help on how to get past this would be greatly appreciated.

-- Page or records
DECLARE @p0 int;
DECLARE @p1 int;
SET @p0 = 100;
SET @p1 = 20;

SELECT DISTINCT ZIP_CODE, RowNum
FROM     ( SELECT ROW_NUMBER() OVER (ORDER BY ZIP_CODE) as RowNum, ZIP_CODE
           FROM   ODS.PHP1300_DWH.FACETS_MEMBER
           --WHERE LEFT(ZIP_CODE, 5) NOT IN (SELECT SHORT_ZIP_CODE 
                    --                     FROM DWH.Reference.R_ZIP_CODE)
         ) AS x
WHERE    RowNum BETWEEN @p0 + 1 AND @p0 + @p1
ORDER BY RowNum

-------------------------------------------------------------------------------------

-- Count
SELECT COUNT(ZIP_CODE)
FROM   ODS.PHP1300_DWH.FACETS_MEMBER  
WHERE  LEFT(ZIP_CODE, 5) NOT IN (SELECT SHORT_ZIP_CODE 
                                 FROM   DWH.Reference.R_ZIP_CODE)

Answer 1

I think that your predicate in the derived table is just quite expensive. Hard to say without an execution plan. Here are a couple of measures you can take:

• Try making LEFT(FACETS_MEMBER.ZIP_CODE, 5) a computed column and index it
• Be sure that R_ZIP_CODE.SHORT_ZIP_CODE has an index on it
• Be sure that R_ZIP_CODE.SHORT_ZIP_CODE has a NOT NULL constraint on it.

Apart from that, I think that your DISTINCT keyword in the outer query is useless, as you're adding the RowNum , which is distinct for every record anyway. So you should move DISTINCT into your nested query, which should use DENSE_RANK() instead of ROW_NUMBER() , as explained here:

http://blog.jooq.org/2013/10/09/sql-trick-row_number-is-to-select-what-dense_rank-is-to-select-distinct/