如何在mysql查询中连接行

Question

table 1
--------
pid | name
1    someone
2    another


table2
--------
bid | valu
1     drum
2     guitar
3     flower
4     cake


table3
------
id | pid | bid | pref
1    1     3     yes
2    1     1     maybe
3    1     2     no
4    2     4     definately
5    2     2   
6    2     3     no

So as you can see I have 3 simple tables where the third one is used to create a mapping between table 1 and 2 along with some additional data. Now I need to write a query to display the valu and pref in a concatenated string based on the pid ,

So against pid = 1 , the expected output is something like flower yes, drum maybe, guitar no ....so How do I write this query?

I tried( pretty much a blind guess):

SELECT opa.name, GROUP_CONCAT(CONCAT(opb.valu,' ',opc.pref) SEPARATOR ',') AS myChoice
 From
     table_1 opa
 INNER JOIN table_3 opc ON opc.pid = opa.pid
 INNER JOIN table_2 opb ON opb.bid = opc.bid

Any help is appreciated.

Answer 1

your query is right you just forgot the GROUP BY

 SELECT opa.name, GROUP_CONCAT(CONCAT(opb.valu,' ',opc.pref) SEPARATOR ',') AS myChoice
 From
 table1 opa
 INNER JOIN table3 opc ON opc.pid = opa.pid
 INNER JOIN table2 opb ON opb.bid = opc.bid
 group by opc.pid

DEMO HERE