Select statement inside CASE - SQL

Question

I am trying to figure out the right code for the below logic. If there is a certain value in the first column, display the value from the second column for that specific record. Can someone please help? Thanks.

CASE WHEN TableA.Column1 = 'a' THEN 'select TableA.Column2 '
     WHEN TableA.Column4 = 'b' THEN 'select TableA.Column5'

     ELSE TableA.Column6
END AS [Test]

Answer 1

You were almost there just remove the select from case statement. Since all the values are coming from same table no need of select in case statement just keep column name it will fetch the corresponding column value.

SELECT CASE
         WHEN Column1 = 'a' THEN Column2
         WHEN Column4 = 'b' THEN Column5
         ELSE Column6
       END AS [Test]
FROM   tableA