Avoid multiple Case When - MySQL

Question

I have a query: Select , myfunction(param1, ) FROM table Both the Case When instances are the same set of conditions. So here I am clearly repeating the same conditions. Question: Is there a way to not repeat the same Case When block efficiently?

nbk · Answer

For this you can use user defined Varaible
Select @res := CASE WHEN A = 1 then a END, myfunction(param1, @res)
FROM table1;

Or in mysql 8
WITH myselectanswer as
(Select  CASE WHEN A = 1 then a END myresult
FROM table1)
Select myselectanswer.myresult, myfunction(param1, myselectanswer.myresult)
FROM myselectanswer

Avoid multiple Case When - MySQL

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