Wildcards and escape characters in SQLServer

The wildcard in SQL is used to replace one or more characters. Use the SQL wildcard with the LIKE operator. The common wildcard % in SQLServer matches any length (the length can be 0) characters such as m % n matching characters m and n with any character strings. The matching examples include man, min, mon, moon ,... _ match any single character, as shown in figure

The wildcard in SQL is used to replace one or more characters. Use the SQL wildcard with the LIKE operator. The common wildcard % in SQL Server matches any length (the length can be 0) characters, for example, m % n matches any character between m and n, matching examples include man, min, mon, moon ,... _ match any single character, as shown in figure

Wildcard

The wildcard character in SQL is used to replace one or more characters.

Use the SQL wildcard with the LIKE operator.

Common wildcards in SQL Server

%

Match any length (the length can be 0) characters

For example,'m % n' matches any character string between characters m and n. The matching examples include man, min, mon, moon ,...

_

Match any single character

For example,'m _ n' matches strings with any character between characters m and n. The matching examples include man, min, mon ,...

[Character Set combination]

Match any character in the character set

For example, '[mz]' matches the character m or z, '[m-z]' matches any single character between m and z.

[^]

Match any single character not in parentheses

For example, '[^ mz]' matches any single character that is not m or z.

Escape characters

Using escape characters, you can tell DBMS that the wildcard in the query is no longer a wildcard, but the actual value of the character.

For example, after "%" is escaped using the escape character, "%" indicates the percentage.

Use ESCAPE to define ESCAPE characters

See the following example:

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Create table tb_TestTable (

Id int not null identity,

Name NVARCHAR (64 ),

Primary key (id ));

Insert into tb_TestTable (name) VALUES ('tiana ');

Insert into tb_TestTable (name) VALUES ('tiana5 ');

Insert into tb_TestTable (name) VALUES ('tiana5% ');

SELECT name FROM tb_TestTable WHERE name LIKE '%/%' ESCAPE 'HTTP: // www.3lian.com /'

In this example, we first define the table tb_TestTable, insert three data records into the table, and then query the table.

In the LIKE '%/%' ESCAPE 'HTTP: // www.3lian.com/'clause in the query, 'HTTP: // response. Of course, the first percent is still a wildcard. Therefore, the query result here should be: 'tiana5% '.

In SQL SERVER, if you do not use the ESCAPE clause to define ESCAPE characters, you can also use '[%]' to tell DNMS: Here, % is no longer a wildcard but a percent sign.

Therefore, the preceding query can also be written as follows:

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SELECT name FROM tb_TestTable WHERE name LIKE '% [%]'

The above description also applies to other wildcard characters, as well as single quotation marks and double quotation marks.