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

Not in MySQL. I tried it and I get the following error:

ERROR 1054 (42S22): Unknown column 'a' in 'field list'