使用GROUP_CONCAT查詢

Question

我對mysql查詢沒有什麼問題。我需要GROUP_CONCAT中的GROUP_CONCAT之類的東西。 LOOK：

數據庫設計：

SELECT cid, country, capital, 
    GROUP_CONCAT(DISTINCT mid, '=',city SEPARATOR '|*|') AS data 
FROM t1 
    INNER JOIN t2 ON t2.c_id = t1.cid 
    INNER JOIN t3 ON t2.c_id = t3.mid 
WHERE t1.cid =1 

返回

[cid] => 1 
[country] => France 
[capital] => Paris 
[data] => 1=Lyon|*|2=Chartres|*|3=Valence 

但我想加盟此查詢表T4（我沒有想法如何做到這一點）和如果輸出看起來像這樣會很好

[cid] => 1 
[country] => France 
[capital] => Paris 
[data] => 1=Lyon=|*|2=Chartres=Max#Alex#Frank|*|3=Valence=John 

ps。 t4.m_id = t3.mid

Answer 1

我不知道是什麼原因，你會想這樣做在SQL，但這裏是一個返回所需結果的版本：

SELECT t1.cid, 
    t1.country, 
    t1.capital, 
    GROUP_CONCAT(DISTINCT t34.mid,"=", t34.city, "=", t34.names ORDER BY t34.mid SEPARATOR "|*|")AS data 
FROM table1 t1 
INNER JOIN table2 t2 
    ON t1.cid = t2.c_id 
LEFT JOIN 
(
    select t3.mid, t3.city, 
    Coalesce(GROUP_CONCAT(DISTINCT t4.names SEPARATOR "#"), '') names 
    from table3 t3 
    left join table4 t4 
    on t3.mid= t4.m_id 
    group by t3.mid, t3.city 
) t34 
    ON t2.city_id = t34.mid 
where t1.cid = 1 
group by t1.cid, t1.country 

見SQL Fiddle with Demo

結果：

| CID | COUNTRY | CAPITAL |            DATA | 
--------------------------------------------------------------------------------- 
| 1 | France | Paris | 1=Lyon=|*|2=Chartes=Max#Alex#Frank|*|3=Valence=John | 

Answer 2

您的數據模型非常混亂......我的意思是t2.city_id = t3s.mid ......嚴重嗎？

總之，這裏的一個解決方案：

SELECT cid, country, capital, GROUP_CONCAT(city_list SEPARATOR "|*|") AS data 
FROM (
    SELECT mid, CONCAT(mid, "=", city, "=", COALESCE(names_list, "")) AS city_list 
    FROM (
    SELECT m_id, GROUP_CONCAT(names SEPARATOR '#') AS names_list 
    FROM t4 
    GROUP BY m_id 
) AS t4s 
    RIGHT JOIN t3 ON t3.mid = t4s.m_id 
) AS t3s 
JOIN t2 ON t2.city_id = t3s.mid 
JOIN t1 ON t1.cid = t2.c_id 
GROUP BY cid 

結果：

| CID | COUNTRY | CAPITAL |             DATA | 
---------------------------------------------------------------------------------- 
| 1 | France | Paris | 1=Lyon=|*|2=Chartres=Max#Alex#Frank|*|3=Valence=John | 

View on SQLfiddle

Answer 3

SQL Fiddle進行測試。

select distinct cid,country,capital, 
group_concat(distinct t3.mid,"=",city, '=', coalesce(names, '') separator "|*|") as data 
from t1 
inner join t2 on t2.c_id = t1.cid 
inner join t3 on t2.city_id = t3.mid 
left join (select m_id, group_concat(names separator '#') as names 
      from t4 
      group by m_id) t5 on t3.mid = t5.m_id 
where t1.cid =1;