Try this:Create Trigger [dbo].[IT_Restrict_AreaCodes]ON [dbo].[dialempty]AFTER INSERTASBEGINupdate dialemptyset phonenum = '1111111111'from dialempty inner join inserted on dialempty.[PRIMARYKEY] = inserted.[PRIMARYKEY] inner join project on dialempty.ProjectID = project.ProjectIDwhere project.projecttype = 2 and Left(dialempty.phonenum,3) IN (203,475,860,959,406,218,320,507,612,651,763,952)END
...and consider making your trigger fire on both insert and update.