1、官方文档：
count：COUNT(expr) [over_clause]
https://dev.mysql.com/doc/refman/8.0/en/group-by-functions.html#function_count
1.1 实例：
select update_time,sid,group_concat(if(age > ‘1‘, tid, NULL)),count(DISTINCT if(age =1,tid,null)) as current_t
from tb_s_members group by update_time,sid order by update_time desc
2、group_concat 官方文档：
GROUP_CONCAT([DISTINCT] expr [,expr ...] [ORDER BY {unsigned_integer | col_name | expr} [ASC | DESC] [,col_name ...]] [SEPARATOR str_val])
https://dev.mysql.com/doc/refman/8.0/en/group-by-functions.html#function_group-concat
Mysql count(1) group_concat 高级用法(count 过滤条件，group_concat过滤条件)
原文：https://www.cnblogs.com/cbugs/p/9340751.html