如何在SQL Server中使用LIKE运算符找到'%'？

Question

我有一个列名称Address,其中包含一些地址,其中'%'位于:

Address
--------------------
Aman Ja%lan%
Stree% Ro%ad

等等

如何编写LIKE运算符来查找该模式？

我试过了:

declare @var char(1)
set @var='!%'
select Address from Accomodation where Address like '%'+@var+'%'

Answer 1

I would use

WHERE columnName LIKE '%[%]%'

SQL Server stores string summary statistics for use in estimating the number of rows that will match a LIKE clause. The cardinality estimates can be better and lead to a more appropriate plan when the square bracket syntax is used.

The response to this Connect Item states

We do not have support for precise cardinality estimation in the presence of user defined escape characters. So we probably get a poor estimate and a poor plan. We'll consider addressing this issue in a future release.

An example

CREATE TABLE T
(
X VARCHAR(50),
Y CHAR(2000) NULL
)

CREATE NONCLUSTERED INDEX IX ON T(X)

INSERT INTO T (X)
SELECT TOP (5) '10% off'
FROM master..spt_values
UNION ALL
SELECT  TOP (100000)  'blah'
FROM master..spt_values v1,  master..spt_values v2


SET STATISTICS IO ON;
SELECT *
FROM T 
WHERE X LIKE '%[%]%'

SELECT *
FROM T
WHERE X LIKE '%\%%' ESCAPE '\'

显示第一个查询的457个逻辑读取和第二个查询的50,003个逻辑读取.

Answer 2

你可以使用ESCAPE:

WHERE columnName LIKE '%\%%' ESCAPE '\'

• SQLFiddle演示