问题
$query=$this->db
->select(a.date,group_concat(s.name)
->from("tbl_attendance a,tbl_students s")
->WHERE ("FIND_IN_SET(s.student_id, a.attendance)")->group_by("a.date")
->get();
I wanted to know whether I have used the FIND_IN_SET and group_by functions correctly. Thanks in advance
回答1:
FIND_IN_SET() returns the position of a string if it is present (as a substring) within a list of strings
so you should search if a value is != 0
eg:
->where("FIND_IN_SET(s.student_id, a.attendance) !=", 0)
->group_by("a.date")
来源：https://stackoverflow.com/questions/43295235/usage-of-find-in-set-in-query