在我正在查询的一个表中，聚集索引是在非主键的键上创建的。 （我不知道为什么。）
但是，该表的主键有一个非聚集索引。
在执行计划中，SQL 选择聚集索引，而不是我在查询中使用的主键的非聚集索引。
SQL 这样做有什么原因吗？如何强制 SQL 选择非聚集索引？
追加更多细节：
表有很多字段，查询包含很多联接。让我抽象一下。
表定义如下所示：
SlowTable
[SlowTable_id] [int] IDENTITY(200000000,1) NOT NULL,
[fk1Field] [int] NULL,
[fk2Field] [int] NULL,
[other1Field] [varchar] NULL,
etc. etc...
然后该表的索引是：
fk1Field (Clustered)
SlowTable_id (Non-Unique, Non-Clustered)
fk2Field (Non-Unique, Non-Clustered)
... and 14 other Non-Unique, Non-Clustered indices on other fields
据推测，针对 fk1Field 进行了更多查询，这就是为什么他们选择它作为聚集索引的基础。
我的查询使用视图：
SELECT
[field list]
FROM
SourceTable1 S1
INNER JOIN SourceTable2 S2
ON S2.S2_id = S1.S2_id
INNER JOIN SourceTable3 S3
ON S3.S3_id = S2.S3_id
INNER JOIN SlowTable ST
ON ST.SlowTable_id = S1.SlowTable_id
INNER JOIN [many other tables, around 7 more...]
执行计划比较大，涉及的节点说
Hash Match
(Inner Join)
Cost: 9%
有一个粗箭头指向
Clustered Index Scan (Clustered)
SlowTable.fk1Field
Cost: 77%
我希望这能提供有关该问题的足够详细信息。
Thanks!
附录 2：
对我之前帖子的更正。该视图没有 where 子句。它只是一系列内部联接。执行计划取自在复杂查询中使用视图（列为 SLOW_VIEW）的 Insert 语句，如下所示：
（此存储过程的作用是根据权重对某些记录的总量进行按比例分割，权重计算为占总数的百分比。这模仿了将一个值从一个帐户分配到其他帐户的情况。）
INSERT INTO dbo.WDTD(
FieldA,
FieldB,
GWB_id,
C_id,
FieldC,
PG_id,
FieldD,
FieldE,
O_id,
FieldF,
FieldG,
FieldH,
FieldI,
GWBIH_id,
T_id,
JO_id,
PC_id,
PP_id,
FieldJ,
FieldK,
FieldL,
FieldM,
FieldN,
FieldO,
FieldP,
FieldQ,
FieldS)
SELECT DISTINCT
@FieldA FieldA,
GETDATE() FieldB,
@Parameter1 GWB_id,
GWBIH.C_id C_id,
P.FieldT FieldC,
P.PG_id PG_id,
PAM.FieldD FieldD,
PP.FieldU FieldE,
GWBIH.O_id O_id,
CO.FieldF FieldF,
CO.FieldG FieldG,
PSAM.FieldH FieldH,
PSAM.FieldI FieldI,
SOURCE.GWBIH_id GWBIH_id,
' ' T_id,
GWBIH.JO_id JO_id,
SOURCE.PC_id PC_id,
GWB.PP_id,
SOURCE.FieldJ FieldJ,
1 FieldK,
ROUND((SUM(GWBIH.Total) / AGG.Total) * SOURCE.Total, 2) FieldL,
ROUND((SUM(GWBIH.Total) / AGG.Total) * SOURCE.Total, 2) FieldM,
0 FieldN,
' ' FieldO,
ESGM.FieldP_flag FieldP,
SOURCE.FieldQ FieldQ,
'[UNPROCESSED]'
FROM
dbo.Table1 GWBIH
INNER JOIN dbo.Table2 GWBPH
ON GWBPH.GWBP_id = GWBIH.GWBP_id
INNER JOIN dbo.Table3 GWB
ON GWB.GWB_id = GWBPH.GWB_id
INNER JOIN dbo.Table4 P
ON P.P_id = GWBPH.P_id
INNER JOIN dbo.Table5 ESGM
ON ESGM.ET_id = P.ET_id
INNER JOIN dbo.Table6 PAM
ON PAM.PG_id = P.PG_id
INNER JOIN dbo.Table7 O
ON O.dboffcode = GWBIH.O_id
INNER JOIN dbo.Table8 CO
ON
CO.Country_id = O.Country_id
AND CO.Brand_id = O.Brand_id
INNER JOIN dbo.Table9 PSAM
ON PSAM.Office_id = GWBIH.O_id
INNER JOIN dbo.Table10 PCM
ON PCM.PC_id = GWBIH.PC_id
INNER JOIN dbo.Table11 PC
ON PC.PC_id = GWBIH.PC_id
INNER JOIN dbo.Table12 PP
ON PP.PP_id = GWB.PP_id
-- THIS IS THE VIEW THAT CONTAINS THE CLUSTERED INDEX SCAN
INNER JOIN dbo.SLOW_VIEW GL
ON GL.JO_id = GWBIH.JO_id
INNER JOIN (
SELECT
GWBIH.C_id C_id,
GWBPH.GWB_id,
SUM(GWBIH.Total) Total
FROM
dbo.Table1 GWBIH
INNER JOIN dbo.Table2 GWBPH
ON GWBPH.GWBP_id = GWBIH.GWBP_id
INNER JOIN dbo.Table10 PCM
ON PCM.PC_id = GWBIH.PC_id
WHERE
PCM.Split_flag = 0
AND GWBIH.JO_id IS NOT NULL
GROUP BY
GWBIH.C_id,
GWBPH.GWB_id
) AGG
ON AGG.C_id = GWBIH.C_id
AND AGG.GWB_id = GWBPH.GWB_id
INNER JOIN (
SELECT
GWBIH.GWBIH_id GWBIH_id,
GWBIH.C_id C_id,
GWBIH.FieldQ FieldQ,
GWBP.GWB_id GWB_id,
PCM.PC_id PC_id,
CASE
WHEN WT.FieldS IS NOT NULL
THEN WT.FieldS
WHEN WT.FieldS IS NULL
THEN PCMS.FieldT
END FieldJ,
SUM(GWBIH.Total) Total
FROM
dbo.Table1 GWBIH
INNER JOIN dbo.Table2 GWBP
ON GWBP.GWBP_id = GWBIH.GWBP_id
INNER JOIN dbo.Table4 P
ON P.P_id = GWBP.P_id
INNER JOIN dbo.Table10 PCM
ON PCM.PC_id = GWBIH.PC_id
INNER JOIN dbo.Table11 PCMS
ON PCMS.PC_id = PCM.PC_id
LEFT JOIN dbo.WT WT
ON WT.ET_id = P.ET_id
AND WT.PC_id = GWBIH.PC_id
WHERE
PCM.Split_flag = 1
GROUP BY
GWBIH.GWBI_id,
GWBIH.C_id,
GWBIH.FieldQ,
GWBP.GWB_id,
WT.FieldS,
PCM.PC_id,
PCMS.ImportCode
) SOURCE
ON SOURCE.C_id = GWBIH.C_id
AND SOURCE.GWB_id = GWBPH.GWB_id
WHERE
PCM.Split_flag = 0
AND AGG.Total > 0
AND GWBPH.GWB_id = @Parameter1
AND NOT EXISTS (
SELECT *
FROM dbo.WDTD
WHERE
TD.C_id = GWBIH.C_id
AND TD.FieldA = GWBPH.GWB_id
AND TD.JO_id = GWBIH.JO_id
AND TD.PC_id = SOURCE.PC_id
AND TD.GWBIH_id = ' ')
GROUP BY
GWBIH.C_id,
P.FieldT,
GWBIH.JO_id,
GWBIH.O_id,
GWBPH.GWB_id,
P.PG_id,
PAM.FieldD,
PP.FieldU,
GWBIH.O_id,
CO.FieldF,
CO.FieldG,
PSAM.FieldH,
PSAM.FieldI,
GWBIH.JO_id,
SOURCE.PC_id,
GWB.PP_id,
SOURCE.FieldJ,
ESGM.FieldP_flag,
SOURCE.GWBIH_id,
SOURCE.FieldQ,
AGG.Total,
SOURCE.Total
附录 3：在视图的 select 语句上执行执行计划时，我看到以下内容：
Hash Match <==== Bitmap <------ etc...
(Inner Join) (Bitmap Create)
Cost: 0% Cost: 0%
^
|
|
Parallelism Clustered Index Scan (Clustered)
(Repartition Streams) <==== Slow_Table.fk1Field
Cost: 1% Cost: 98%
附录 4：我想我发现了问题。聚集索引扫描并不是指我引用主键的子句，而是指另一个需要一个在某种程度上与上面的 fk1Field 相关的字段的子句。
