database - SQL Server 2005 以不同的顺序索引相同的列

Question

我有一份需要很长时间才能执行的报告。我运行了数据库引擎调优顾问，其中一项建议是创建 2 个索引。但是，我注意到索引是相同的列，但顺序不同。

这是表格:

---Locations---
| *LocationID |
| Code        |
| ...more...  |
| DivisionID  |
| RegionID    |
---------------

建议添加这两个索引

CREATE NONCLUSTERED INDEX [IX_Locations_Region_Loc_Div] ON [dbo].[Locations] 
(
    [RegionID] ASC,
    [LocationID] ASC,
    [DivisionID] ASC
)
INCLUDE ( [Code]) WITH (SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF) ON [PRIMARY]
GO

CREATE NONCLUSTERED INDEX [IX_Locations_Loc_Reg_Div] ON [dbo].[Locations] 
(
    [LocationID] ASC,
    [RegionID] ASC,
    [DivisionID] ASC
)
INCLUDE ( [Code]) WITH (SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF) ON [PRIMARY]
GO

当 SQL Server 只用于内部连接时，为什么 SQL Server 需要以不同的顺序排列这 3 个列的索引？

SELECT UserID, LocationID FROM [User] u INNER JOIN [Locations] l ON u.LocationID = l.LocationID

Answer 1

它不会用于您包含的 SQL。它必须考虑其他查询才能做出该推荐。