Method of querying comma separated strings in a field by MySQL

mysql A way to query a comma separated string in a field

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Preface

Now there are the following scenes . We have a case table . Each case corresponds to multiple tags , One tag corresponds to one case . When we do paging at the front desk , Multiple tags need to be matched
The data structure of the table is as follows

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One 、 First, let's talk about a requirement

We need to find out crowd_label_id by 4,6,9 All of the case_id 4,6,9 Is and condition

1. First, find the corresponding case_id All satisfied labels That is, row to column Use GROUP_CONCAT function
2. After the query, we will know the corresponding case_id All the labels .
3. The rest is if according to label_id To make a match . That's when we can use it mysql function FIND_IN_SET To match whether the specified label exists in the string . Of course, this step can also be put into the program to make judgments .
   
   The result is a perfect match label_id contain 4,9 All of the case_id

Enclosed sql

SELECT * FROM (
SELECT case_id,GROUP_CONCAT(crowd_label_id) AS aa FROM weapp_case_label WHERE crowd_label_id IN (4,6,9) GROUP BY case_id
) AS aaa WHERE  FIND_IN_SET('4', aa) AND FIND_IN_SET('9', aa) 

summary

The main knowledge here is mysql Row column of , There are multiple rows of data that can be displayed in a column .