from [table] when [new column is notnull]

Question

I have written a query for select some results from different tables with a union all. After the from you can use the where. In that where I want to use a column that I 'made' in the query. How can I do this?

example

 SELECT    
    [column1] AS 'K1', 
    ISNULL([column2], 'else')  + ' ' + ISNULL([column3], 'else') AS 'K2'    
 FROM 
    [table]  
 FULL JOIN
    [table] ON A.Name = C.AccountIdName 
 WHERE
    A.Name IS NOT NULL  
    AND K1 IS NOT NULL

Is that possible to take the K1 and set in into the where? Or is there an other option?

---

UPDATE: New example

SELECT    
        [column1] AS 'K1', 
        ISNULL([column2], 'else')  + ' ' + ISNULL([column3], 'else') AS 'K2'    
     FROM 
        [table]  
     FULL JOIN
        [table] ON A.Name = C.AccountIdName 
     WHERE
        A.Name IS NOT NULL  
        **AND K1 IS NOT NULL
        AND K3 IS NOT NULL**

UNION ALL

SELECT    
        [column1] AS 'K1', 
        ISNULL([column2], 'else')  + ' ' + ISNULL([column3], 'else') AS 'K2'    
     FROM 
        [table]  
     FULL JOIN
        [table] ON A.Name = C.AccountIdName 
     WHERE
        A.Name IS NOT NULL  
        **AND K2 IS NOT NULL 
        AND K4 IS NOT NULL**

As you can see I want in the first select K1 en K3 and in the second I want K2 end K4

I hope you can solve this problem too, this was a good solution.

SELECT * FROM 
(
 SELECT [column1] as 'K1' , ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
 FROM [table] full join [table] on A.Name = C.AccountIdName where A.Name IS NOT NULL
) 
res WHERE res.K1 IS NOT NULL

Answer 1

You can use it, but as a result of your subquery

SELECT * FROM 
(
 SELECT [column1] as 'K1' , ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
 FROM [table] full join [table] on A.Name = C.AccountIdName where A.Name IS NOT NULL
) 
res WHERE res.K1 IS NOT NULL

UPDATED

SELECT * FROM 
(
   SELECT [column1] as 'K1' , ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
   FROM [table] full join [table] on A.Name = C.AccountIdName where A.Name IS NOT NULL
) 
res1 WHERE res1.K1 IS NOT NULL AND res1.K3 IS NOT NULL
UNION ALL
SELECT * FROM 
(
   SELECT [column1] as 'K1' , ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
   FROM [table] full join [table] on A.Name = C.AccountIdName where A.Name IS NOT NULL
) 
res2 WHERE res2.K2 IS NOT NULL AND res2.K4 IS NOT NULL //BUT DOES IT HAS K4???

Answer 2

Unfortunately, you can't use the ALIAS on the WHERE clause that was created on the same level. There are two options that can do:

Use the original column:

SELECT  [column1] as 'K1' , 
        ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
FROM    [table] full join [table] 
          on A.Name = C.AccountIdName 
where   A.Name IS NOT NULL AND [column1] IS NOT NULL

Or wrap it with subquery:

SELECT K1, K2
FROM
(
    SELECT  [column1] as 'K1' , 
            ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
    FROM    [table] full join [table] 
              on A.Name = C.AccountIdName
    where   A.Name IS NOT NULL
) s
WHERE K1 IS NOT NULL

Answer 3

You'll need to use a subquery or CTE:

;WITH CTE AS
(
 SELECT    
    [column1] AS 'K1', 
    ISNULL([column2], 'else')  + ' ' + ISNULL([column3], 'else') AS 'K2'    
 FROM 
    [table]  
 FULL JOIN
    [table] ON A.Name = C.AccountIdName 
 WHERE
    A.Name IS NOT NULL
) 
SELECT    
   K1, K2
FROM 
   CTE
WHERE
   K1 IS NOT NULL

Answer 4

You can check for Column1 instead of K1 since K1 is alias name hence cannot be used in where condition. Like:

SELECT 
    [column1] as 'K1' , 
    ISNULL([column2], 'else') + ' ' + ISNULL([column3], 'else') as 'K2' 
FROM [table] full join [table] on A.Name = C.AccountIdName 
where 
    A.Name IS NOT NULL AND 
    [column1] IS NOT NULL