Question

Is it possible to do the following pseudo-code in Postgres 8+ or generic SQL?

SELECT table1.a, table1.b ... table1.x, (IF table1.x > table1.y RETURN table1.y ELSE return table1.x AS table1.y), table1.z...

Answer 1

LEAST is a good solution in this case, but the more generic conversion would be the CASE statement

SELECT 
    table1.a,
    table1.b,
    ... 
    table1.x, 
    CASE WHEN table1.x > table1.y THEN table1.y ELSE table1.x END AS y,
    table1.z
    ...