Use calculated values from subquery in another variable

问题

I have a complicated sub query that displays [Days Open]. I want to use this [Days Open] as a value in a another variable. Here is a simplified code example.

If I take the entire subselect and paste it wherever the second subselect=[days open] the query works it just takes 3 min.

I just want the second subquery to reference the calculated value from the first subquery

     SELECT 
Sub.Category AS 'Category',
    SubSelect(not actually value just shortening code) As [Days Open],

(Case 
When Sub.Category Like '%Part%' Then 
    (Case 
    When Cast([Days Open] As Int)>60 Then 'Late' 
    When Cast([Days Open] As Int)<61 Then 'Not Late'
    Else 'N/A' End)
When Sub.Category Like '%Determination%' Then 
    (Case 
    When Cast([Days Open] As Int)>1 Then 'Late' 
    When Cast([Days Open] As Int)<2 Then 'Not Late'
    Else 'N/A' End)
When Sub.Category Like '%History%' Then 
    (Case 
    When Cast([Days Open] As Int)>5 Then 'Late' 
    When Cast([Days Open] As Int)<6 Then 'Not Late'
    Else 'N/A' End)
When Sub.Category Like '%Eval%' Then 
    (Case 
    When Cast([Days Open] As Int)>45 Then 'Late' 
    When Cast([Days Open] As Int)<46 Then 'Not Late'
    Else 'N/A' End)
Else 'N/A' End) As 'Days Open Late'*/

    FROM Tasks As Sub
    WHERE (Sub.Status=2) And ((Sub.DateClosed Between '04/01/2013' And '04/30/2013 11:59:59 PM')) 
    Order By Sub.Category Asc, 'Days Open' Desc

回答1:

I would move the SubSelect down into the FROM clause, trating it like a virtual table. That way you can refence its value multiple times within the SELECT clause.

来源：https://stackoverflow.com/questions/16487587/use-calculated-values-from-subquery-in-another-variable

标签

sql

subquery