在LIKE中转义通配符 [英] Escaping wildcards in LIKE

问题描述

在Oracle中使用SQL LIKE运算符时如何转义通配符(_和%)?

How do I escape wildcards (_ and %) when using a SQL LIKE operator in Oracle?

我今天遇到一个愚蠢的问题.我需要使用LIKE在varchar列上搜索下划线_的存在.正如预期的那样，它不起作用-因为根据SQL，下划线是通配符.这是我的(简化)代码:

I came to a silly issue today. I need to search for the presence of an underscore _ on a varchar column using LIKE. It doesn't work -- as expected -- since underscores are wildcards according to SQL. Here's my (simpified) code:

create table property (
  name varchar(20),
  value varchar(50)
);

insert into property (name, value) values ('port', '8120');
insert into property (name, value) values ('max_width', '90');
insert into property (name, value) values ('taxrate%', '5.20');

我在PostgreSQL中尝试了以下查询，它们返回了我想要的行:

I tried the following queries in PostgreSQL and they return the rows I want:

select * from property where name like '%\_%'; -- should return: max_width

select * from property where name like '%\%%'; -- should return: taxrate%

不幸的是，它在Oracle 12c中不起作用.有没有通配符转义的标准"方法?还是至少在Oracle中有效?

Unfortunately it doesn't work in Oracle 12c. Is there a "standard" way of escaping wildcards? Or at least something that works in Oracle?

推荐答案

您可以使用

You can use the escape syntax

您可以使用ESCAPE子句在模式中包含实际字符%或_，该子句标识转义字符.如果转义字符在模式中的字符%或_之前，则Oracle会在模式中按字面意义解释该字符，而不是将其解释为特殊的模式匹配字符.

You can include the actual characters % or _ in the pattern by using the ESCAPE clause, which identifies the escape character. If the escape character precedes the character % or _ in the pattern, then Oracle interprets this character literally in the pattern rather than as a special pattern-matching character.

因此您可以这样做:

select * from property where name like '%\_%' escape '\';

NAME                 VALUE                                             
-------------------- --------------------------------------------------
max_width            90                                                

select * from property where name like '%\%%' escape '\';

NAME                 VALUE                                             
-------------------- --------------------------------------------------
taxrate%             5.20                                              

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