Note the use of the database

· GROUP_CONCAT () function may be the value of the same field in multiple records grouped, spliced ​​into a record returned. But by default, the maximum splice length is limited, resulting in incomplete results.

You can use sql query maximum length:

show variables like 'group_concat_max_len';

 

Sql modify the maximum length may be used:

SET GLOBAL group_concat_max_len = 4294967295;
SET SESSION group_concat_max_len = 4294967295;

 

· Mysql generally used to fuzzy query Like statement, but lower efficiency Like statement, easily lead to a full table scan; the other statements is a full table scan, can not query the index, so you need to change in order to improve the efficiency of database queries