MySQL string interception and interception characters for query

Use some string interception functions that come with mysql to process the data. The following is the string interception and interception characters I compiled for query.

1. String interception in MySQL
There are special string interception functions in MySQL: there are two commonly used ones: substring_index(str,delim,count ) and concat
1.substring_index(str,delim,count) functions are commonly used.
The order inside the function brackets is: the string to be separated and intercepted (such as: "aaa_bbb_ccc"), the delimiter (such as: "_"), and the position (indicating which delimiter is located, such as: " 1").
If count is a positive number, then counting starts from the left, and the function returns the string to the left of the count-th separator;
If count is a negative number, then counting starts from the right, and the function returns the count-th separator Everything on the right;
count can be 0 and returned is empty.

例子：substring_index("aaa_bbb_ccc","_",1) ，返回为 aaa；
         substring_index("aaa_bbb_ccc","_",2) ，返回为 aaa_bbb；
         substring_index(substring_index("aaa_bbb_ccc","_",-2),"_",1) ，返回为 bbb；

2.concat is to connect several strings
Example: concat('m','y','s','q','l');
Return: mysql
2. Query all data containing this character based on a field in the table
1.find_in_set: SELECT * FROM user WHERE find_in_set('Wu', name);
Query all data in the user table whose name contains "Wu"
2.REGEXP: SELECT * FROM user WHERE name REGEXP '('WHERE'|'Liu')';
Use regular rules, Query the data containing Liu or Wu

The above is the MySQL string interception and interception characters I compiled for query. I hope it will be helpful to everyone in the future

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