SQL 条件唯一约束与同一表中的 Where 子句

Question

我有一个表，我想确保五列的组合在该表中保持唯一。例如：

ALTER TABLE [dbo].[MyTable] 
    ADD CONSTRAINT [UQ__MyTable.MFG.Model.Class.Depiction.Iteration] 
        UNIQUE NONCLUSTERED 
        (
         [ManufacturerID] ASC,
         [Model] ASC,
         [BlockClassID] ASC,
         [BlockDepictionID] ASC,
         [BlockIterationID] 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

我想排除第六个单独列具有特定值的组合。例如，我只想在列 [Flag] = 0 时强制执行上述约束，并在列 [Flag] = 1 时排除强制执行。

Answer 1

作为解决方法，您可以通过创建唯一的筛选索引在 SQL Server 2008 及更高版本中获得正确的 ANSI 行为。

CREATE UNIQUE NONCLUSTERED INDEX [IX__MyTable.MFG.Model.Class.Depiction.Iteration] 
ON [dbo].[MyTable] ([ManufacturerID],[Model],[BlockClassID],[BlockDepictionID],[BlockIterationID])
WHERE [Flag] = 0;

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