Question

I’m trying to set ROW_NUMBER()… as an alias so I can reference it in the OFFSET. e.g. OFFSET some_alias - 1. I need to get a single row including the ROW_NUMBER() from a larger query. Here’s my working code (gets correct ROW_NUMBER(), but isn’t offset by the right amount):

WITH FirstQuery AS (
    SELECT "RepInitials", COUNT("OrderStatus"), ROW_NUMBER()OVER(ORDER BY COUNT("OrderStatus") DESC)
    FROM "tblBulkSalesQuery"
    WHERE "OrderStatus" = 'CMC'
    GROUP BY "RepInitials"
)
SELECT "RepInitials", COUNT("OrderStatus"), ROW_NUMBER()OVER(ORDER BY COUNT("OrderStatus") DESC)
    FROM "tblBulkSalesQuery"
    WHERE "OrderStatus" = 'CMC'
    GROUP BY "RepInitials"
    LIMIT 1
    OFFSET 1;

Answer 1

select *
from (
    SELECT "RepInitials", 
           COUNT("OrderStatus") as order_status_count, 
           ROW_NUMBER() OVER (ORDER BY COUNT("OrderStatus") DESC) as rn
    FROM "tblBulkSalesQuery"
    WHERE "OrderStatus" = 'CMC'
    GROUP BY "RepInitials"
) as t
where rn = 1

Edit:

The t is an alias for the nested select (“derived table”). PostgreSQL requires each derived table to get it’s own “name” and that can only be done by assigning a alias.

It’s pretty much the same as:

with t as (
  ... here goes the real select ...
)
select *
from t 
where rn = 1;