Question

I have to migrate some SQL from PostgreSQL to SQL Server (2005+). On PostgreSQL i had:

select count(id) as count, date
from table 
group by date 
order by count 
limit 10 offset 25

Now i need the same SQL but for SQL Server. I did it like below, but get error: Invalid column name 'count'. How to solve it ?

select * from (
   select row_number() over (order by count) as row, count(id) as count, date 
   from table 
   group by date
) a where a.row >= 25 and a.row < 35

Answer 1

You can’t reference an alias by name, at the same scope, except in an ending ORDER BY (it is an invalid reference inside of a windowing function at the same scope).

To get the exact same results, it may need to be extended to (nesting scope for clarity):

SELECT c, d FROM 
(
  SELECT c, d, ROW_NUMBER() OVER (ORDER BY c) AS row FROM 
  (
    SELECT d = [date], c = COUNT(id) FROM dbo.table GROUP BY [date]
  ) AS x
) AS y WHERE row >= 25 AND row < 35;

This can be shortened a little bit as per mohan’s answer.

SELECT c, d FROM 
(
  SELECT COUNT(id), [date], ROW_NUMBER() OVER (ORDER BY COUNT(id))
   FROM dbo.table GROUP BY [date]
) AS y(c, d, row)
WHERE row >= 25 AND row < 35;

In SQL Server 2012, it’s much easier with OFFSET / FETCH – closer to the syntax you’re used to, but actually using ANSI-compatible syntax rather than proprietary voodoo.

SELECT c = COUNT(id), d = [date]
FROM dbo.table GROUP BY [date]
ORDER BY COUNT(id)
OFFSET 25 ROWS FETCH NEXT 10 ROWS ONLY;

I blogged about this functionality in 2010 (lots of good comments there too) and should probably invest some time doing some serious performance tests.

And I agree with @ajon – I hope your real tables, columns and queries don’t abuse reserved words like this.