Summary on the use of REGEXP regular expressions in MySQL
In the past, I used like to find data. Later, I found that there are regular expressions in mysql and I feel that the performance is better than like. Now I will share with you a detailed explanation of the use of mysql REGEXP regular expressions. I hope this method will be helpful to everyone. .
Regular expression describes a set of strings. The simplest regular expression is one that does not contain any special characters. For example, the regular expression hello matches hello.
Non-trivial regular expressions adopt a special structure that allows them to match more than one string. For example, the regular expression hello|word matches the string hello or the string word.
As a more complex example, the regular expression B[an]*s matches any of the following strings: Bananas, Baaaaas, Bs, and any string starting with B, ending with s, and ending with Any other string containing any number of a or n characters.
The following are the schemas available for tables with the REGEXP operator.
Application example, find user records with incorrect email format in the user table:
SELECT * FROM users WHERE email NOT REGEXP '^[A-Z0-9._%-]+@[A-Z0-9.-]+.[A-Z]{2,4}$'
Regular expression in MySQL database The grammar of formula mainly includes the meaning of various symbols.
(^) character
matches the starting position of the string, such as "^a" means a string starting with the letter a.
mysql> select 'xxxyyy' regexp '^xx'; +-----------------------+ | 'xxxyyy' regexp '^xx' | +-----------------------+ | 1 | +-----------------------+ 1 row in set (0.00 sec)
Query whether the xxxyyy string starts with xx. The result value is 1, which means the value is true and the condition is met.
($) character
matches the end position of the string, such as "X^" means a string ending with the letter X.
(.) Character
This character is the dot in English. It matches any character, including carriage return, line feed, etc.
(*) character
The asterisk matches 0 or more characters, and there must be content before it. For example:
mysql> select 'xxxyyy' regexp 'x*';
This SQL statement, the regular match is true.
(+) character
The plus sign matches 1 or more characters, and there must also be content before it. The plus sign is used similarly to the asterisk, except that the asterisk is allowed to appear 0 times, and the plus sign must appear at least once.
(?) character
question mark matches 0 or 1 times.
Example:
Now based on the above table, various types of SQL queries can be installed to meet the requirements. Here are some understandings. Consider we have a table as person_tbl and there is a field named name:
Query to find all names starting with 'st'
mysql> SELECT name FROM person_tbl WHERE name REGEXP '^st';
Query to find all The name ends with 'ok'
mysql> SELECT name FROM person_tbl WHERE name REGEXP 'ok$';
Query to find all the name strings containing 'mar'
mysql> SELECT name FROM person_tbl WHERE name REGEXP 'mar';
Query to find all names starting with a vowel and ending with 'ok'
mysql> SELECT name FROM person_tbl WHERE name REGEXP '^[aeiou]|ok$';
The following reserved words can be used in a regular expression
^
The matched string starts with the following string
mysql> select "fonfo" REGEXP "^fo$"; -> 0(表示不匹配) mysql> select "fofo" REGEXP "^fo"; -> 1(表示匹配)
$
The matched string ends with the previous string
mysql> select "fono" REGEXP "^fono$"; -> 1(表示匹配) mysql> select "fono" REGEXP "^fo$"; -> 0(表示不匹配) .
Matches any character (including new lines)
mysql> select "fofo" REGEXP "^f.*"; -> 1(表示匹配) mysql> select "fonfo" REGEXP "^f.*"; -> 1(表示匹配)
a*
Match any number of a (including empty string)
mysql> select "Ban" REGEXP "^Ba*n"; -> 1(表示匹配) mysql> select "Baaan" REGEXP "^Ba*n"; -> 1(表示匹配) mysql> select "Bn" REGEXP "^Ba*n"; -> 1(表示匹配)
a+
Match any number of a (excluding empty string)
mysql> select "Ban" REGEXP "^Ba+n"; -> 1(表示匹配) mysql> select "Bn" REGEXP "^Ba+n"; -> 0(表示不匹配)
a?
Matches one or zero a
mysql> select "Bn" REGEXP "^Ba?n"; -> 1(表示匹配) mysql> select "Ban" REGEXP "^Ba?n"; -> 1(表示匹配) mysql> select "Baan" REGEXP "^Ba?n"; -> 0(表示不匹配)
de|abc
matches de or abc
mysql> select "pi" REGEXP "pi|apa"; -> 1(表示匹配) mysql> select "axe" REGEXP "pi|apa"; -> 0(表示不匹配) mysql> select "apa" REGEXP "pi|apa"; -> 1(表示匹配) mysql> select "apa" REGEXP "^(pi|apa)$"; -> 1(表示匹配) mysql> select "pi" REGEXP "^(pi|apa)$"; -> 1(表示匹配) mysql> select "pix" REGEXP "^(pi|apa)$"; -> 0(表示不匹配)
(abc)*
Match any number of abc (including empty string)
mysql> select "pi" REGEXP "^(pi)*$"; -> 1(表示匹配) mysql> select "pip" REGEXP "^(pi)*$"; -> 0(表示不匹配) mysql> select "pipi" REGEXP "^(pi)*$"; -> 1(表示匹配)
{1}
{2,3}
This is a more comprehensive method, which can realize the functions of several previous reserved words
a *
can be written as a{0,}
a+
can be written as a{1,}
a?
can be written as a{0,1}
There is only one integer parameter i in {}, which means that the character can only appear i times; there is one integer parameter i in {}, followed by ", ", indicating that the character can appear i times or more than i times; there is only one integer parameter i within {}, followed by a ",", and then an integer parameter j, indicating that the character can only appear i times or more, j times The following (including i times and j times). The integer parameter must be greater than or equal to 0 and less than or equal to RE_DUP_MAX (default is 255). If there are two parameters, the second must be greater than or equal to the first
[a-dX]
matches "a", "b", "c", "d" or " "
"[", "]" must be used in pairs
mysql> select "aXbc" REGEXP "[a-dXYZ]"; -> 1(表示匹配) mysql> select "aXbc" REGEXP "^[a-dXYZ]$"; -> 0(表示不匹配) mysql> select "aXbc" REGEXP "^[a-dXYZ]+$"; -> 1(表示匹配) mysql> select "aXbc" REGEXP "^[^a-dXYZ]+$"; -> 0(表示不匹配) mysql> select "gheis" REGEXP "^[^a-dXYZ]+$"; -> 1(表示匹配) mysql> select "gheisa" REGEXP "^[^a-dXYZ]+$"; -> 0(表示不匹配)
Related recommendations:
JS regular expression perfectly realizes the ID card verification function
How to use regular expressions to highlight JavaScript code
javascript matches the regular expression code commented in js
The above is the detailed content of Summary on the use of REGEXP regular expressions in MySQL. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Big data structure processing skills: Chunking: Break down the data set and process it in chunks to reduce memory consumption. Generator: Generate data items one by one without loading the entire data set, suitable for unlimited data sets. Streaming: Read files or query results line by line, suitable for large files or remote data. External storage: For very large data sets, store the data in a database or NoSQL.

MySQL query performance can be optimized by building indexes that reduce lookup time from linear complexity to logarithmic complexity. Use PreparedStatements to prevent SQL injection and improve query performance. Limit query results and reduce the amount of data processed by the server. Optimize join queries, including using appropriate join types, creating indexes, and considering using subqueries. Analyze queries to identify bottlenecks; use caching to reduce database load; optimize PHP code to minimize overhead.

Backing up and restoring a MySQL database in PHP can be achieved by following these steps: Back up the database: Use the mysqldump command to dump the database into a SQL file. Restore database: Use the mysql command to restore the database from SQL files.

How to insert data into MySQL table? Connect to the database: Use mysqli to establish a connection to the database. Prepare the SQL query: Write an INSERT statement to specify the columns and values to be inserted. Execute query: Use the query() method to execute the insertion query. If successful, a confirmation message will be output.

One of the major changes introduced in MySQL 8.4 (the latest LTS release as of 2024) is that the "MySQL Native Password" plugin is no longer enabled by default. Further, MySQL 9.0 removes this plugin completely. This change affects PHP and other app

To use MySQL stored procedures in PHP: Use PDO or the MySQLi extension to connect to a MySQL database. Prepare the statement to call the stored procedure. Execute the stored procedure. Process the result set (if the stored procedure returns results). Close the database connection.

Creating a MySQL table using PHP requires the following steps: Connect to the database. Create the database if it does not exist. Select a database. Create table. Execute the query. Close the connection.

Oracle database and MySQL are both databases based on the relational model, but Oracle is superior in terms of compatibility, scalability, data types and security; while MySQL focuses on speed and flexibility and is more suitable for small to medium-sized data sets. . ① Oracle provides a wide range of data types, ② provides advanced security features, ③ is suitable for enterprise-level applications; ① MySQL supports NoSQL data types, ② has fewer security measures, and ③ is suitable for small to medium-sized applications.
