747b0392__5_1___Postgres_OnLine_Journal__Microsoft_SQL_Server_2008
[Feature] Dynamic and action SQL in functions [MySQL 5.1] No, but can in Stored procedures which aren't callable from SELECT statements so more limiting than PostgreSQL [PostgreSQL 8.4] Yes! - you can do really cool things with action functions in SELECT statements [Microsoft SQL Server 2008] 
No - but you can in Stored procedures but you can't call stored procs from SELECT statements so much more limiting than PostgreSQL
Cross Compare of PostgreSQL 8.4, SQL Server 2008, MySQL 5.1 - Postgres OnLine Journal
Microsoft SQL Server 2008