假设我有一个Foo带有列的表ID1, ID2和一个over定义的复合主键ID2, ID1。（我目前正在使用System Center产品，该产品具有以这种方式定义的多个表，并且主键列以与表定义中出现的相反顺序列出。）
CREATE TABLE dbo.Foo(
ID1 int NOT NULL,
ID2 int NOT NULL,
CONSTRAINT [PK_Foo] PRIMARY KEY CLUSTERED (ID2, ID1)
);
GO
-- Add a row and update stats so that histogram isn't empty
INSERT INTO Foo (ID1, ID2) VALUES (1,2);
UPDATE STATISTICS dbo.Foo;中的key_ordinal列以sys.index_columns在复合主键中声明的顺序显示索引列：
SELECT t.name, i.name, c.column_id, c.name, ic.index_column_id, ic.key_ordinal
FROM sys.tables AS t
JOIN sys.indexes AS i
ON t.[object_id] = i.[object_id]
JOIN sys.index_columns AS ic
ON ic.[object_id] = i.[object_id]
AND ic.index_id = i.index_id
JOIN sys.columns AS c
ON ic.column_id = c.column_id
AND ic.[object_id] = c.[object_id]
WHERE t.name = 'Foo';
直方图还以相同顺序显示统计信息：
DBCC SHOW_STATISTICS ('Foo',PK_Foo);
但是，sys.stats_columns显示的列以相反的顺序（ID1, ID2）。
SELECT s.name, sc.stats_column_id, c.name
FROM sys.stats AS s
JOIN sys.stats_columns AS sc
ON s.stats_id = sc.stats_id
AND s.[object_id] = sc.[object_id]
JOIN sys.columns AS c
ON c.[object_id] = s.[object_id]
AND c.column_id = sc.column_id
JOIN sys.objects AS o
ON o.[object_id] = c.[object_id]
WHERE o.name = 'Foo'
AND s.name = 'PK_Foo';
联机丛书说这stats_column_id是“一组统计信息列中的基于1的序数”，因此我期望值1指向统计对象的第一列。
这是sys.stats_columns我的错误还是误解？
我已验证此行为在当前版本的SQL Server 2005、2008、2008 R2、2012和2014上发生。
sys.stats_columns 在其他情况下，它似乎反映了统计对象内的顺序，例如：
CREATE TABLE dbo.Foo2(
ID1 int NOT NULL,
ID2 int NOT NULL,
ID3 int NULL,
String VARCHAR(10) NULL,
CONSTRAINT [PK_Foo2] PRIMARY KEY CLUSTERED (ID2, ID1)
);
GO
INSERT INTO Foo2 (ID1, ID2, ID3, String) VALUES (1,2,3,'String');
CREATE STATISTICS ST_Test ON Foo2 (ID3, String);
CREATE STATISTICS ST_Test2 ON Foo2 (String, ID3);
DBCC SHOW_STATISTICS ('Foo2',ST_Test);
DBCC SHOW_STATISTICS ('Foo2',ST_Test2);
SELECT s.name, sc.stats_column_id, c.name
FROM sys.stats AS s
JOIN sys.stats_columns AS sc
ON s.stats_id = sc.stats_id
AND s.[object_id] = sc.[object_id]
JOIN sys.columns AS c
ON c.[object_id] = s.[object_id]
AND c.column_id = sc.column_id
JOIN sys.objects AS o
ON o.[object_id] = c.[object_id]
WHERE o.name = 'Foo2'
AND s.name LIKE 'ST_Test%';
这是另一个示例，其中sys.stats_columns似乎返回正确的数据，这一次是针对索引的统计信息：
--drop table dbo.Foo3
CREATE TABLE dbo.Foo3(
ID1 int NOT NULL,
ID2 int NOT NULL,
ID3 int NULL,
String VARCHAR(10) NULL,
CONSTRAINT [PK_Foo3] PRIMARY KEY CLUSTERED (ID2, ID1)
);
GO
INSERT INTO Foo3 (ID1, ID2, ID3, String) VALUES (1,2,3,'String');
UPDATE STATISTICS Foo3;
CREATE INDEX IX_Test ON Foo3 (ID3, String);
CREATE INDEX IX_Test2 ON Foo3 (String, ID3);
DBCC SHOW_STATISTICS ('Foo3',IX_Test);
DBCC SHOW_STATISTICS ('Foo3',IX_Test2);
SELECT s.name, sc.stats_column_id, c.name
FROM sys.stats AS s
JOIN sys.stats_columns AS sc
ON s.stats_id = sc.stats_id
AND s.[object_id] = sc.[object_id]
JOIN sys.columns AS c
ON c.[object_id] = s.[object_id]
AND c.column_id = sc.column_id
JOIN sys.objects AS o
ON o.[object_id] = c.[object_id]
WHERE o.name = 'Foo3'
AND s.name LIKE 'IX_Test%';
也许您应该为此提交Microsoft Connect项目？对我来说似乎是越野车。
—
Max Vernon
stats_column_idinsys.stats_columns似乎并没有按照它说的去做。因为您要支持索引，所以我坚持使用索引列顺序。如果您只是看统计对象，那么它似乎index_col()是当前最好的选择