如何簡化多個子查詢和GROUP_CONCAT？

Question

這個查詢得到我我想要的結果，從一個主表米，三個次級表小號，Ø和d與三個查找表LS幫助，LO和LD ，但是它爲每個字段查詢每個表一次。

SELECT m.id, 
(SELECT GROUP_CONCAT(s.field1 SEPARATOR ', ') 
    FROM s, ls 
    WHERE ls.mid=m.id AND ls.sid=s.id) 
    AS s_field, 
(SELECT GROUP_CONCAT(o.field1 SEPARATOR ', ') 
    FROM o, lo 
    WHERE lo.mid=m.id AND lo.oid=o.id) 
    AS o_field1, 
(SELECT GROUP_CONCAT(o.field2 SEPARATOR ', ') 
    FROM o, lo 
    WHERE lo.mid=m.id AND lo.oid=o.id) 
    AS o_field2, 
(SELECT GROUP_CONCAT(o.field3 SEPARATOR ', ') 
    FROM o, lo 
    WHERE lo.mid=m.id AND lo.oid=o.id) 
    AS o_field3, 
(SELECT GROUP_CONCAT(o.field4 SEPARATOR ', ') 
    FROM o, lo 
    WHERE lo.mid=m.id AND lo.oid=o.id) 
    AS o_field4, 
(SELECT GROUP_CONCAT(d.field1 SEPARATOR ', ') 
    FROM d, ld 
    WHERE ld.mid=m.id AND ld.did=d.id) 
    AS d_field1, 
(SELECT GROUP_CONCAT(d.field2 SEPARATOR ', ') 
    FROM d, ld 
    WHERE ld.mid=m.id AND ld.did=d.id) 
    AS d_field2 
FROM m 
WHERE m.id=22 GROUP BY m.id 

如何重寫它以獲得相同的結果，但每個表只有一個子查詢。

Answer 1

您可以使用以下方法：

SELECT m.id, 
    GROUP_CONCAT(sls.field1 SEPARATOR ', ') AS s_field, 
    GROUP_CONCAT(olo.field1 SEPARATOR ', ') AS o_field1, 
    GROUP_CONCAT(olo.field2 SEPARATOR ', ') AS o_field2, 
    GROUP_CONCAT(olo.field3 SEPARATOR ', ') AS o_field3, 
    GROUP_CONCAT(olo.field4 SEPARATOR ', ') AS o_field4, 
    GROUP_CONCAT(dld.field1 SEPARATOR ', ') AS d_field1, 
    GROUP_CONCAT(dld.field2 SEPARATOR ', ') AS d_field2, 
FROM m 
(
    SELECT ls.mid, s.field1 
    FROM s 
    INNER JOIN ls 
     on s.id = ls.sid 
) sls 
    on m.id = sls.mid 
INNER JOIN 
(
    SELECT lo.mid, o.field1, o.field2, o.field3, o.field4 
    FROM o 
    INNER JOIN lo 
     on o.id = lo.oid 
) olo 
    on m.id = olo.mid 
INNER JOIN 
(
    SELECT ld.mid, d.field1, d.field2 
    FROM d 
    INNER JOIN ld 
     on d.id = ld.did 
) dld 
    on m.id = dld.mid 
WHERE m.id=22 
GROUP BY m.id