Sql server SQLServer中where子句中使用函数（IS_成员）时的基数估计警告_Sql Server_Sql Server 2012_Type Conversion_Sql Execution Plan

Sql server SQLServer中where子句中使用函数（IS_成员）时的基数估计警告

sql-server sql-server-2012

Sql server SQLServer中where子句中使用函数（IS_成员）时的基数估计警告,sql-server,sql-server-2012,type-conversion,sql-execution-plan,Sql Server,Sql Server 2012,Type Conversion,Sql Execution Plan,考虑以下场景测试数据 CREATE TABLE T1 ( COL1 numeric (6, 0) NOT NULL, COL2 numeric (18, 0) NOT NULL, COL3 numeric (18, 0) NOT NULL, COL4 numeric (5, 0) NOT NULL, COL5 numeric (18, 0) NOT NULL, COL6 varchar (20) NOT N

考虑以下场景

测试数据

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

场景1:

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

--执行计划警告--

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

表达式

中的类型转换（CONVERT_IMPLICIT（nvarchar（20），[V9WEBDB1].[V9WEBDB1].[T3].[COL10]，0））可能会影响查询计划选择中的“CardinalityEstimate”

场景2

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

--执行计划警告：

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

表达式中的类型转换（CONVERT_IMPLICIT（nvarchar（20），[V9WEBDB1].[V9WEBDB1].[T3].[COL10]，0））可能会影响查询计划选择中的“CardinalityEstimate”

场景3

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

执行计划警告--无

询问：

CREATE TABLE   T1 (
     COL1   numeric (6, 0) NOT NULL,
     COL2   numeric (18, 0) NOT NULL,
     COL3   numeric (18, 0) NOT NULL,
     COL4   numeric (5, 0) NOT NULL,
     COL5   numeric (18, 0) NOT NULL,
     COL6   varchar (20) NOT NULL,
     COL7   varchar (50) NULL,
     COL8   numeric (1, 0) NULL,
     COL9   numeric (18, 0) NULL,
     COL10   varchar (20) NULL 
 ) 

ALTER TABLE  T1    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_1',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_2',    '000002',   0,  NULL,   'admin_group')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_3',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_4',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_5',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_6',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_7',    '000002',   0,  NULL,   'QABrowns')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_8',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_9',    '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_10',   '000002',   0,  NULL,   'SuperUser')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_11',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_12',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_13',   '000002',   0,  NULL,   'LOLCOP2')

INSERT INTO  T1 VALUES (1,  2,  12, 1,  11, 'COL_14',   '000002',   0,  NULL,   'LOLCOP2')

 SELECT T1.* from  T1 
    WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T3  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T3    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )
UPDATE STATISTICS  T3   
INSERT INTO  T3 SELECT * FROM  T1 WHERE COL10 IN ('LOLCOP2','QABrowns','SuperUser')

UPDATE STATISTICS  T3

SELECT T3.* from  T3 
WHERE IS_MEMBER( COL10)=1

SELECT * INTO  T4  FROM  T1 WHERE COL10 IN ('admin_group')
ALTER TABLE  T4    
ADD PRIMARY KEY ( COL1,COL2, COL3,  COL4,  COL5, COL6    )

UPDATE STATISTICS  T4   

SELECT T4.* from  T4 
WHERE IS_MEMBER( COL10)=1

在第一和第二场景中

SELECT T1.* from  T1 WHERE IS_MEMBER( COL10)=1

sql给出了以下警告

表达式中的类型转换（CONVERT_IMPLICIT（nvarchar（20），[V9WEBDB1].[V9WEBDB1].[T3].[COL10]，0））可能会影响查询计划选择中的“CardinalityEstimate”

但在第三种情况下

SELECT T1.* from  T1 WHERE IS_MEMBER( COL10)=1

sql不会给出任何警告

COL10的数据类型是varchar（20）

服务器排序规则：SQL\u拉丁1\u通用\u CP1\u CI\u AS

1）为什么会出现此警告？
2）如何避免上述警告

1）为什么会出现这种警告

您的表列

col10

是

varchar（20）

，但

is_MEMBER（）

接受

sysname

作为参数，因此服务器将

varchar（20）

转换为

nvarchar（20）

（

sysname

是

nvarchar（128）

）

2）如何避免上述警告

将您的

col10

类型更改为

sysname

或至少更改为

nvarchar（20）

感谢测试数据，我在sql 2016上尝试过（家中没有2012）无法重新设置此问题