Invalid column name error in WHERE clause, column selected with CASE

Question

I have a (rather complicated) SQL statement where I select data from lots of different tables, and to cope with a bad legacy data structure, I have a couple of custom colum

Answer 1

You can use a CTE - something like

WITH CTE AS
(
SELECT 
     ..., 
     CASE channel 
         WHEN 1 THEN channel_1 
         WHEN 2 THEN channel_2 
         ... 
         ELSE 0 
     END AS ChannelValue, 
     CASE channelu 
         WHEN 1 THEN channelu_1 
         WHEN 2 THEN channelu_2 
         ... 
         ELSE '0' 
     END AS ChannelWithUnit, 
     ... 
 FROM  
)
SELECT * 
FROM CTE
WHERE ChannelValue > Limit * p.Percentage / 100