这将只包括
User.FirstName与
Provider.ProviderID最终结果集:
SELECt User.FirstName, Provider.ProviderID FROM User LEFT OUTER JOIN Provider ON User.ProviderID = Provider.ID

这将只包括
User.FirstName与
Provider.ProviderID最终结果集:
SELECt User.FirstName, Provider.ProviderID FROM User LEFT OUTER JOIN Provider ON User.ProviderID = Provider.ID