Shulou(Shulou.com)05/31 Report--

This article mainly introduces "how to use MySQL REGEXP". In daily operation, I believe many people have doubts about how to use MySQL REGEXP. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "how to use MySQL REGEXP". Next, please follow the editor to study!

1. About NULL

The normal comparison operator is used for NULL, and the result returned is NULL.

Mysql > select 0 = null, 1 null, 2 > null, 3

= null, 5 null | 3

= null | 5 select 0 is null, null is null

+-+ +

| | 0 is null | null is null | |

+-+ +

| | 0 | 1 |

+-+ +

1 row in set (0.00 sec)

Mysql > select 0 is not null, null is not null

+-+ +

| | 0 is not null | null is not null | |

+-+ +

| | 1 | 0 |

+-+ +

1 row in set (0.00 sec)

Mysql > select 0 null, null null

+-+ +

| | 0 null | null null | |

+-+ +

| | 0 | 1 |

+-+ +

1 row in set (0.00 sec)

In MySQL, NULL is different from a null value.

Mysql > select''IS NULL

+-+

| |''IS NULL |

+-+

| | 0 |

+-+

1 row in set (0.00 sec)

2.REGEXP

The REGEXP operator can perform more complex string comparison operations, mainly through regular expressions. Regular expressions consist of a mixture of standard characters and metacharacters that specifically define matching patterns. The following table lists the metacharacters that are often used in regular expressions:

Metacharacter action

+ matches the values of one or more preceding characters

* match the values of 0 or more preceding characters

? Match the values of 0 or 1 characters before

. Match any character

^ matches the beginning of the string

$matches the end of the string

S matches a single white space character, including tabulation matching newline characters

S matches all characters except white space characters

D matches numbers between 0 and 9

W matches letters, numbers, and descending characters

W matching uses any character that w cannot match

Mysql > select 'google' regexp' go+ogle', 'google' regexp' go*ogle', 'google' reg

Exp 'go?ogle'

+

-+

| | 'google' regexp' go+ogle' | 'google' regexp' go*ogle' | 'google' regexp' go?og |

Le' |

+

-+

| | 1 | 1 |

1 |

+

-+

1 row in set (0.00 sec)

Mysql > select 'google' regexp' go+gle', 'google' regexp' go*gle', 'google' regex

P 'go?gle'

+-

-+

| | 'google' regexp' go+gle' | 'google' regexp' go*gle' | 'google' regexp' go?gle' |

| |

+-

-+

| | 1 | 1 | 0 |

| |

+-

-+

1 row in set (0.00 sec)

Mysql > select 'google' regexp' gooo+gle', 'google' regexp' gooo*gle', 'google' r

Egexp 'gooo?gle'

+-

-+

| | 'google' regexp' gooo+gle' | 'google' regexp' gooo*gle' | 'google' regexp' goo |

Overngle' |

+-

-+

| | 0 | 1 |

1 |

+-

-+

1 row in set (0.00 sec)

Mysql > select 'google' regexp' ^ goo', 'google' regexp' goo$'

+-+-

| | 'google' regexp' ^ goo' | 'google' regexp' goo$' |

+-+-

| | 1 | 0 |

+-+-

1 row in set (0.00 sec)

Mysql > select 'google' regexp' ^ gle', 'google' regexp' gle$'

+-+-

| | 'google' regexp' ^ gle' | 'google' regexp' gle$' |

+-+-

| | 0 | 1 |

+-+-

1 row in set (0.00 sec)

Mysql > select 'fifi' regexp' ^ fi', 'fifi' regexp' fi$', 'fifi' regexp' ^ fi$', 'f

Ifi' regexp'^ fifi$'

+-

-+

| | 'fifi' regexp' ^ fi' | 'fifi' regexp' fi$' | 'fifi' regexp' ^ fi$' | 'fifi' rege |

Xp'^ fifi$' |

+-

-+

| | 1 | 1 | 0 | |

1 |

+-

-+

1 row in set (0.00 sec)

3. System information function

Here are some common system information functions:

User () or system_user () returns the current login user name

Connection_id () returns the connection ID of the current user

Database () returns the current database name

Version () returns the version of the MySQL server

Mysql > select user (), connection_id (), database (), version ()

+-+

| | user () | connection_id () | database () | version () |

+-+

| | root@localhost | 2 | ggyy | 5.1.34-community | |

+-+

1 row in set (0.40 sec)

Undefinedundefinedundefinedundefinedundefined

At this point, the study on "how to use MySQL REGEXP" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.