mysql——find_ in_ Set usage

MySQL In the manual find_in_set Syntax explanation of function ：

FIND_IN_SET(str,strlist)

str String to query
strlist Field name Parameter with ”,” Separate Such as (1,2,6,8,10,22)
Query field (strlist) Contained in the (str) Result , The return result is null Or record

If the string str In by N A list of strings composed of sub chains strlist in , Then the return value range is 1 To N Between . A list of strings is a list of characters that are ‘,’ A string consisting of sub chains separated by symbols . If the first parameter is a constant string , And the second is type SET Column , be FIND_IN_SET() Functions are optimized , Use bit calculation . If str be not in strlist or strlist Is an empty string , The return value is 0 . If any parameter is NULL, The return value is NULL. This function contains a comma in the first argument (‘,’) Will not work properly .

It's ok if you don't understand the concept , Sub category by ：

Example 1：

SELECT FIND_IN_SET('b', 'a,b,c,d');

because b stay strlist Put in the collection 2 The location of from 1 Start

select FIND_IN_SET(‘1’, ‘1’); return Namely 1 By this time strlist The set is a little special There is only one string In fact, it requires the previous string Be sure to return greater than... In the latter string collection 0 Number of numbers

select FIND_IN_SET('2', '1,2');    /* return 2*/
select FIND_IN_SET('6', '1');    /* return 0 strlist Does not exist in the str, So back 0.*/

find_in_set() and in The difference between ：

Get a test chart to show the difference between the two

CREATE TABLE `tb_test` (
 `id` int(8) NOT NULL auto_increment,
 `name` varchar(255) NOT NULL,
 `list` varchar(255) NOT NULL,
 PRIMARY KEY (`id`)
);
INSERT INTO `tb_test` VALUES (1, 'name', 'daodao,xiaohu,xiaoqin');
INSERT INTO `tb_test` VALUES (2, 'name2', 'xiaohu,daodao,xiaoqin');
INSERT INTO `tb_test` VALUES (3, 'name3', 'xiaoqin,daodao,xiaohu');

I thought mysql You can do this query ：

SELECT id,name,list from tb_test WHERE 'daodao' IN(list); -- ( One )

In fact, this is not the case , This is only when list The value of the field is equal to ’daodao’ when （ and IN The preceding string exactly matches ）, The query is valid , Otherwise, there will be no results , Even if ’daodao’ It's really list in .

Let's take a look at this ：

SELECT id,name,list from tb_test WHERE 'daodao' IN ('libk', 'zyfon', 'daodao'); -- ( Two )

This is OK .

What's the difference between these two ？ Why can't Article 1 get the right result , And the second one can get results . The reason is （ One ） in (list) list It's a variable. , and （ Two ） in (‘libk’, ‘zyfon’, ‘daodao’) Is a constant .

So if we want to let （ One ） Can work correctly , Need to use

find_in_set(): 
SELECT id,name,list from tb_test WHERE FIND_IN_SET('daodao',list);     -- ( One ) Improved version 

summary ：

So if list Is a constant , You can use IN, Otherwise, use find_in_set() function .

These are the two sql Yes, the effect of query is the same ：

SELECT * from C_PURCHASINGMASTERDATA where FIND_IN_SET(EKGRP,'C54,C02,C14,C60,C06,C61,C53,C51,C12,C08,C03,C07')
SELECT * from C_PURCHASINGMASTERDATA where EKGRP in ('C54','C02','C14','C60','C06','C61','C53','C51','C12','C08','C03','C07')

But if the second sentence sql The values inside are passed in sql A variable field of , So the second sentence sql It's not easy to use . It should be decided on the basis of the actual situation in Or use it find_in_set() function .

find_in_set() and like The difference between ：

The main difference is like Is a broad range of fuzzy queries , and find_in_set() It's an exact match , And... Is used between field values ‘,' Separate .

Now I want to query the role number 2 Users of , use like Keyword query ：

SELECT userid,username,userrole  role  FROM `user` WHERE userrole LIKE '%2%';

result ：

use find_in_set() Inquire about ：

SELECT userid,username,userrole  role  FROM `user` WHERE find_in_set('2',userrole)

result ：

Obviously with find_in_set() The query result is the result we want . So their

The main difference is like Is a broad range of fuzzy queries ; and find_in_set() It's an exact match , And... Is used between field values ‘,' Separate ,Find_IN_SET The result of the query should be less than like Result of query .

mysql in find_in_set() and in() Usage comparison

stay mysql in in Can include a specified number , and find_in_set() For specific data types .

find_in_set Function usage

For example ：

There's a list of articles with a type Field , It stores article types , Yes 1 headlines 、2 recommend 、3 hotspot 、4 Image & Text …1,12,13 wait .
Now there's an article that he's both headlines , It's hot again , Or graphics ,
type China and Israel 1,3,4 Format store .
So how do we use sql Find all type There is 4 What about articles with standard graphics and text ？？
That's what we need find_in_set It's time to start .
Here's the quote ：

select * from article where FIND_IN_SET('4',type)

MySQL In the manual find_in_set Syntax of functions ：

FIND_IN_SET(str,strlist)

If the string str In by N List of strings made up of sub chains strlist in , Then the return value range is 1 To N Between .
A list of strings is a list of characters that are ‘,’ A string consisting of sub chains separated by symbols . If the first parameter is a constant string , And the second is type SET Column , be FIND_IN_SET() Functions are optimized , Use bit calculation .
If str be not in strlist or strlist Is an empty string , The return value is 0 . If any parameter is NULL, The return value is NULL. This function contains a comma in the first argument (‘,’) Will not work properly .

mysql> SELECT FIND_IN_SET('b', 'a,b,c,d');

-> 2 because b stay strlist Put in the collection 2 The location of from 1 Start

select FIND_IN_SET(‘1’, ‘1’); return Namely 1 By this time strlist The set is a little special There is only one string In fact, it requires the previous string Be sure to be in the next string set To return to Greater than 0 Number of numbers

select FIND_IN_SET('2', '1,2');  return 2
select FIND_IN_SET('6', '1');  return 0

Be careful ：

select * from treenodes where FIND_IN_SET(id, '1,2,3,4,5');

Use find_in_set Function returns multiple records at a time
id Is the field of a table , And then each record is id be equal to 1,2,3,4,5 When
It's kind of similar in （ aggregate ）

select * from treenodes where id in (1,2,3,4,5);

Get a test chart to show the difference between the two

CREATE TABLE `test` (
`id` int(8) NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`list` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
)
 
INSERT INTO `test` VALUES (1, 'name', 'daodao,www.jb51.net,xiaoqin');
INSERT INTO `test` VALUES (2, 'name2', 'xiaohu,daodao,xiaoqin');
INSERT INTO `test` VALUES (3, 'name3', 'xiaoqin,daodao,www.jb51.net');

I thought MySQL You can do this query :

（ One ）

select id, list, name from table where 'daodao' IN (list);

In fact, this is not the case , This is only when name yes list When the first element in , The query is valid , Otherwise, there will be no results , Even if ’daodao’ It's really list in .
Let's take a look at this ：

（ Two ）

select id, list, name from table where 'daodao' IN ('libk', 'zyfon', 'daodao');

This is OK .

What's the difference between these two ？ Why can't Article 1 get the right result , And the second one can get results .
The reason is （ One ） in (list) list It's a variable. , and （ Two ） in (‘libk’, ‘zyfon’, ‘daodao’) Is a constant .
So if we want to let （ One ） Can work correctly , Need to use find_in_set():

select id, list, name from table where find_in_set('daodao',list);

（ One ） Improved version .

summary ：
So if list Is a constant , You can use IN, Otherwise, use find_in_set() function .

The above is a brief introduction mysql in find_in_set() Function of the use of detailed explanation , I hope that's helpful , If you have any questions, please leave me a message , Xiaobian will reply to you in time . Thank you very much for your support of script House website ！