question

Is a UNIQUE NONCLUSTERED INDEX ok with INCLUDE columns or will it cause performance problems? It possibly has caused performance issues. I do a SELECT statement without a WHERE clause on it. I have always done this SELECT without a WHERE, but now it is causing EVEN MORE performance problems, since I added the INCLUDE columns on the UNIQUE NONCLUSTERED index. I have these indexes both on the same table. The Unique column is not the PK. ALTER TABLE [dbo].[tblContracts] ADD CONSTRAINT [tblContracts$PrimaryKey] PRIMARY KEY CLUSTERED ( [CustomerID] ASC, [StartDate] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] GO CREATE UNIQUE NONCLUSTERED INDEX [tblContracts$PublicIdEtc] ON [dbo].[tblContracts] ( [PublicId] ASC) INCLUDE ( [ContractID] ASC, [CustomerID] ASC, [StartDate] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] GO Another issue is I could change the CLUSTERED index to ContractID, and make the CustomerID/StartDate another NONCLUSTERED UNIQUE (or PK) index, but I tried that and had to go backwards (but maybe that would help too, assuming that I take out the INCLUDE columns on the above UNIQUE index.)