747b0392__5_1___Postgres_OnLine_Journal__Microsoft_SQL_Server_2008
[Feature] UPSERT logic - where you can simultaneously insert if missing and update if present [MySQL 5.1] Yes - via INSERT IGNORE, REPLACE INSERT ON DUPLICATE UPDATE [PostgreSQL 8.4] No [Microsoft SQL Server 2008] 
Yes via MERGE UPDATE
Cross Compare of PostgreSQL 8.4, SQL Server 2008, MySQL 5.1 - Postgres OnLine Journal
Microsoft SQL Server 2008