Usage analysis of regular expression replacement using replace and regexp in MySQL

This article mainly introduces the usage of regular expression using replace and regexp in MySQL, and analyzes the usage techniques and use of replace and regexp regular expression in combination with specific examples. For related notes, friends in need can refer to the following

This article describes the use of replace and regexp for regular expression replacement in MySQL. Share it with everyone for your reference, the details are as follows:

Today a friend asked me if I could modify all the formats similar to "./uploads/110100_cityHotel_Beijing Fu Luxury Hotel.jpg" found in the database. It is in the format of "./uploads/110100cityHotelBeijing Fu Luxury Hotel.jpg". I have never processed data in this way, but I know that mysql can use replace, and regular expressions can also do it.

How to do it?

We only need such a statement,

The code is as follows:

update master_data.md_employee set name=replace(name,"_",'') where id = 825;

-- Note replace(field name, "Character to be replaced", "Character to be replaced"), this is it.

In Mysql, replace and regexp mainly realize data replacement through sql statements.

Let’s first talk about the specific usage of replace.

mysql replace usage

1.replace into

##The code is as follows:

replace into table (id,name) values('1′,'aa'),('2′,'bb')

The function of this statement is to insert two records into the table. If the primary key id is 1 or 2 and does not exist

is equivalent to

The code is as follows:

insert into table (id,name) values('1′,'aa'),('2′,'bb')

If the same value exists, it will not

Insert data
##2.

replace(

object,search,replace)Replace all occurrences of search in object Replace with replace

The code is as follows:

select replace('www.jb51.net','w','Ww')

Example: Replace aa in the name field in the table with bb

The code is as follows:

update table set name=replace(name,'aa','bb')

Other

types of pattern matching provided by MySQL use extended regular expressions.

When you test for matches on such patterns, use the REGEXP and NOT REGEXP

operators (or RLIKE and NOT RLIKE, which are synonyms). Some characters that extend regular expressions are:

· ‘.’ matches any single character.

·

Character Class "[...]" matches any character within square brackets. For example, "[abc]" matches "a", "b", or "c". To name a range of characters, use a "-". "[a-z]" matches any letter, while "[0-9]" matches any number.

· " * " matches zero or more characters preceding it. For example, "x*" matches any number of "x" characters, "[0-9]*" matches any number of digits, and ".*" matches any number of any characters.

The pattern matches if the REGEXP pattern matches anywhere in the value being tested (this is different from LIKE pattern matching, which only matches the entire value).

To position a pattern so that it must match the beginning or end of the value being tested, use "^" at the beginning of the pattern or "$" at the end of the pattern.

To illustrate how extended regular expressions work, let’s rewrite the LIKE

query shown above using REGEXP

: 1. In order to find out what starts with “d For names starting with ", use "^" to match the beginning of the name:

The code is as follows:

SELECT * FROM master_data.md_employee WHERE name REGEXP '^d';

Such a result set is not case-sensitive, if you want to force REGEXP The comparison is case-sensitive, and the BINARY keyword is used to make one of the

strings

into a binary string. This query only matches the first letter of the name, lowercase 'd'.
The code is as follows:

SELECT * FROM master_data.md_employee WHERE name REGEXP BINARY'^d';

To find names ending with "love", use "$" to match the end of the name:

The code is as follows :

SELECT id,name FROM master_data.md_employee WHERE name REGEXP 'love$';

To find names that contain a "w", use the following query:

The code is as follows:

SELECT id,name FROM master_data.md_employee WHERE name REGEXP 'w';

Since if a regular expression appears in Anywhere in the value that the pattern matches, you don't have to put a wildcard on either side of the pattern in the previous query to make it match the entire value, just like you would if you used an SQL pattern.

To find names that contain exactly 5 characters, use "^" and "$" to match the beginning and end of the name, and 5 "." instances in between:

code show as below:

SELECT id,name FROM master_data.md_employee WHERE name REGEXP '^.....$';

你也可以使用“{n}”“重复n次”操作符重写前面的查询：

代码如下:

SELECT id,name FROM master_data.md_employee WHERE name REGEXP '^.{5}$';

这些知识一些简单的mysql的replace和regexp的用法，对于深入的学习，我们会在之后的文章会将具体的例子以及用法写出

The above is the detailed content of Usage analysis of regular expression replacement using replace and regexp in MySQL. For more information, please follow other related articles on the PHP Chinese website!