mysql：在3个表中查询多个记录？

Question

Good day fellow programmers. I have 3 tables, with following sample records.

tbl_members has:

mem_id | mem_fname | mem_lname
  1    |  Ryan     | Layos
  2    |  Dhave    | Sebastian
  3    |  Staven   | Siegal
  4    |  Ma Ethel | Yocop
  5    |  Kelvin   | Salvador
  6    |  Herbert  | Ares

tbl_member_status has:

status_id | mem_id | leader_id | process_id
    1     |   2    |     1     |    2
    2     |   3    |     5     |    3
    3     |   4    |     6     |    4
    4     |   5    |     1     |    4
    5     |   1    |     6     |    4

(tbl_member_status.mem_id is foreign keyed to tbl_members.mem_id, and leader_id is also foreign keyed to tbl_members.mem_id because in my case a member can be a leader. 1 member 1 leader)

tbl_process has:

process_id | process_type
    1      | CONSOLIDATION
    2      | PRE-ENCOUNTER
    3      | ENCOUNTER
    4      | POST-ENCOUNTER

(a member has a process to take which i used enum with values: CONSOLIDATION, PRE-ENCOUNTER, ENCOUNTER, POST-ENCOUNTER, etc.)

My question now is the proper sql query in getting the desired output query like this.

tbl_query_result

   mem_id | member_fname | member_lname | leader_fname | leader_lname | process_type
    2     |  dhave       |  sebastian   |    Ryan      |   Layos      |  PRE-ENCOUNTER
    5     |  Kelvin      |  Salvador    |    Ryan      |   Layos      |  POST-ENCOUNTER

do remember that two columns of tbl_member_status is referring to one column of tbl_members that is mem_id.

UPDATE:

what i have done so far:

SELECT member.mem_fname, member.mem_lname, leader.mem_fname, leader.mem_lname, tbl_process.process_type
FROM 
    tbl_member_status as mem_stats
INNER JOIN 
    tbl_members as member 
INNER JOIN 
    tbl_members as leader 
INNER JOIN 
    tbl_members ON mem_stats.member_id = member.mem_id
INNER JOIN
    tbl_process ON tbl_process.process_id = mem_stats.process_id
WHERE 
    leader.mem_fname = 'Ryan'

This query gets all record even if the leader.mem_fname is not equal to 'Ryan'

Answer 1

Because when you query. The number of rows in the result matters. Like: if your result is for fname = ryan but then the match for mem.id in table memberstatus is two and then in process table is again two. Inshort you will have 2 rows in final output. Can you try this :

Select M.member_fname, M.mem_lname P.process_type from tbl_members M, tbl_member_status MS, tbl_process P where M.mem_id = MS.mem_id and MS.process_id = P.process_id and where M.member_fname = 'ryan'

Okay i misunderstood your question at first. I have a solution for you which will improve your database schema. If one member has only one leader and a single leader has many memebers. Then why not create a different table called leader and connect to members table directly? So it will be a one to one relation. Which will make querying much simpler. So now you have 4 tables.

Select M.member_fname, M.mem_lname, L.fname, L.lname, P.process_type 
from tbl_members M, tbl_member_status MS, tbl_process P, tbl_leader L
where M.leader_id = L.id and M.mem_id = MS.mem_id and MS.process_id = P.process_id and where M.member_fname = 'ryan'