In SQL Server, you can do this in the Query Analazyer (which executes a query and displays the results):

SELECT 'a' AS column1;

You can also do this:
DECLARE @somevariable INT;
SET @somevariable = 1;
SELECT @somevariable;

Can someone translate this to Firebird SQL?

I tried running the queries in the "query analyzer" in Flamerobin but it would not run explaining of an "unexpected end of command"