[英]SQL Server Like Query not case sensitive
Query 询问
SELECT *
from Table_2
WHERE name like ('Joe');
Output 产量
1 100 Joe 2 200 JOE 3 300 jOE 4 400 joe
Why is it not case sensitive? 为什么它不区分大小写?
Problem: 问题:
Query not case sensitive
查询不区分大小写
Cause: Column 'Name' has a case-insensitive ( CI
) collation. 原因:列“名称”具有不区分大小写(
CI
)排序规则。
Solution: You have to use a CS
collation: SELECT * FROM fn_helpcollations() WHERE description LIKE N'%case-sensitive%'
. 解决方案:您必须使用
CS
排序规则: SELECT * FROM fn_helpcollations() WHERE description LIKE N'%case-sensitive%'
。
Note: There is a database collation and column level collation. 注意:存在数据库排序规则和列级排序规则。 And, there is, also, a server level collation.
而且,还有一个服务器级别的排序规则。
SELECT DATABASEPROPERTYEX(DB_NAME(), 'Collation') AS DatabaseCollation
/*
-- Sample output (my database)
DatabaseCollation
----------------------------
SQL_Latin1_General_CP1_CI_AS
*/
SELECT col.collation_name AS ColumnCollation
FROM sys.columns col
WHERE col.object_id = OBJECT_ID(N'dbo.Table_2')
AND col.name = N'Name'
/*
-- Sample output (my database)
ColumnCollation
----------------------------
SQL_Latin1_General_CP1_CI_AS
*/
Simply changing database collation will NOT change the collation for existing user tables and columns: 简单地更改数据库排序规则不会更改现有用户表和列的排序规则:
This statement does not change the collation of the columns in any existing user-defined tables.
此语句不会更改任何现有用户定义表中列的排序规则。 These can be changed by using the COLLATE clause of ALTER TABLE.
可以使用ALTER TABLE的COLLATE子句更改这些内容。
After changing database collation , the output of above queries will be: 更改数据库归类后 ,上述查询的输出将为:
/*
DatabaseCollation -- changed
----------------------------
SQL_Latin1_General_CP1_CS_AS
*/
/*
ColumnCollation -- no change
----------------------------
SQL_Latin1_General_CP1_CI_AS
*/
and, as you can see the collation of column Name
remains CI. 并且,正如您所看到的,列
Name
的排序规则仍为CI。
More, changing database collation will affect only the new created tables and columns. 此外,更改数据库归类将仅影响新创建的表和列。 Thus, changing database collation could generate strange results (in my opinion ) because some
[N][VAR]CHAR
columns will be CI and the new columns will be CS. 因此,更改数据库归类可能会产生奇怪的结果(在我看来 ),因为一些
[N][VAR]CHAR
列将是CI,新列将是CS。
Detailed solution #1: if just some queries for column Name
need to be CS
then I will rewrite WHERE
clause of these queries thus: 详细的解决方案#1:如果只是一些查询列
Name
必须是CS
,然后我会重写WHERE
这些查询的条款这样的:
SELECT Name
FROM dbo.Table_2
WHERE Name LIKE 'Joe' AND Name LIKE 'Joe' COLLATE SQL_Latin1_General_CP1_CS_AS
This will give a change to SQL Server to do an Index Seek
on column Name
(in there is an index on column Name
). 这将使更改SQL服务器做一个
Index Seek
对列Name
(中则列索引Name
)。 Also, the execution plan will include an implicit conversion (see Predicate
property for Index Seek
) because of following predicate Name = N'Joe' COLLATE SQL_Latin1_General_CP1_CS_AS
. 此外,执行计划将包括隐式转换(请参阅
Index Seek
Predicate
属性),因为以下谓词Name = N'Joe' COLLATE SQL_Latin1_General_CP1_CS_AS
。
Detailed solution #2: if all queries for column Name
need to be CS then I will change the collation only for column Name
thus: 详细解决方案#2:如果列
Name
所有查询都需要为CS,那么我将仅更改列Name
的排序规则:
-- Drop all objects that depends on this column (ex. indexes, constraints, defaults)
DROP INDEX IX_Table_2_Name ON dbo.Table_2
-- Change column's collation
ALTER TABLE dbo.Table_2
ALTER COLUMN Name VARCHAR(50) COLLATE SQL_Latin1_General_CP1_CS_AS
-- Replace VARCHAR(50) with proper data type and max. length
-- Replace COLLATE SQL_Latin1_General_CP1_CS_AS with the right CS collation
-- Recreate all objects that depends on column Name (ex. indexes, constraints, defaults)
CREATE INDEX IX_Table_2_Name ON dbo.Table_2 (Name)
-- Test query
SELECT Name
FROM dbo.Table_2
WHERE Name LIKE 'Joe'
If you want your query to be case sensitive on few occasions only, then you can try below query: 如果您希望查询仅在少数情况下区分大小写,那么您可以尝试以下查询:
SELECT *
FROM TableName
where Col1 = 'abcdEfhG' COLLATE SQL_Latin1_General_CP1_CS_AS
Just add "COLLATE SQL_Latin1_General_CP1_CS_AS" in front of the query. 只需在查询前添加“COLLATE SQL_Latin1_General_CP1_CS_AS”即可 。
That is your DB is configured to be case insensitive. 这是您的数据库配置为不区分大小写。
In order to change this: 为了改变这个:
For example, If you are using: 例如,如果您正在使用:
Change it to: 将其更改为:
If you want to understand a bit more about collations, take a look at the accepted answer under this thread. 如果您想了解有关排序规则的更多信息,请查看此主题下的已接受答案。
Update: 更新:
Please Note that as @BogdanSahlean has noted this solution will work for newly created objects but not for existing tables and columns. 请注意,由于@BogdanSahlean已经注意到此解决方案适用于新创建的对象,但不适用于现有的表和列。
From MSDN: 来自MSDN:
You can change the collation of any new objects that are created in a user database by using the COLLATE clause of the ALTER DATABASE statement.
您可以使用ALTER DATABASE语句的COLLATE子句更改在用户数据库中创建的任何新对象的排序规则。 This statement does not change the collation of the columns in any existing user-defined tables.
此语句不会更改任何现有用户定义表中列的排序规则。 These can be changed by using the COLLATE clause of ALTER TABLE.
可以使用ALTER TABLE的COLLATE子句更改这些内容。
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