Whether the Mysql hql string field contains a certain string, use find_in_set

There is such a requirement. In the Mysql database string field (authority), there are values ​​ranging from 1 to N representing different privileges, which are separated by ',', and now we need to extract the list of all members with a certain privilege.

Create the table:

1	CREATE TABLE users(id int(6) NOT NULL AUTO_INCREMENT,PRIMARY KEY (id),name VARCHAR(20) NOT NULL,limits VARCHAR(50) NOT NULL);

adding data:

1	INSERT INTO users(name, limits) VALUES('小张','1,2,12');
2	INSERT INTO users(name, limits) VALUES('小王','11,22,32');

Some fields in Mysql are of string type. How to find records that contain certain characters?

method one:

1	mysql> SELECT * FROM users WHERE limits like "%2%";
2	+----+----+--------+
3	| id |name| limits |
4	+----+----+--------+
5|1|Xiao Zhang|1,2,12|
6	+----+----+--------+
7|2|Xiao Wang|11,22,32|
8	+----+----+--------+
9	2 row in set

In this way, users who do not have permission '2' for the second piece of data are also found, which does not meet expectations. So I checked the manual and used the mysql string function find_in_set().

Method Two:

1	mysql> SELECT * FROM users WHERE find_in_set('2', limits);
2	+----+----+--------+
3	| id |name| limits |
4	+----+----+--------+
5|1|Xiao Zhang|1,2,12|
6	+----+----+--------+
7	1 row in set

This will achieve the effect we expect, and the problem will be solved!

Note: The mysql string function find_in_set(str1, str2) returns the position index of str1 in str2, and str2 must be separated by ",".

It cannot be used directly in hql, but we can use it like this:

from User u where find_in_set('2', limits)>0 ;

That is, '>0' must be included, otherwise an error will be reported.