SQL: Alias Column Name for Use in CASE Statement

Question

Is it possible to alias a column name and then use that in a CASE statement? For example,

SELECT col1 as a, CASE WHEN a = \'test\' THEN \'yes\' END as value          


        

Answer 1

Nor in MsSql

SELECT col1 AS o, e = CASE WHEN o < GETDATE() THEN o ELSE GETDATE() END 
FROM Table1

Returns:

Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.

However if I change to CASE WHEN col1... THEN col1 it works