如何在MAX中使用GROUP_CONCAT（CASE WHEN ...）？

问题描述：

我想从这个查询中得到结果，但我在使用group_concat和max case时遇到了问题。如何在MAX中使用GROUP_CONCAT（CASE WHEN ...）？

SELECT 
    t1.id, 
    t1.name, 
    MAX(CASE WHEN t2.code = t1.f_name THEN t2.name END) AS name2, 
    MAX(CASE WHEN t2.code = t1.l_name THEN t2.name END) AS name3, 
    MAX(CASE WHEN t2.code = t1.a_name THEN t2.name END) AS name4, 
    GROUP_CONCAT(MAX(CASE WHEN FIND_IN_SET(t3.code,t1.vehicles) THEN t3.name END) AS car_owned) 
    GROUP_CONCAT(MAX(CASE WHEN FIND_IN_SET(t3.code,t1.homes) THEN t3.name END) AS home_owned) 
FROM 
    first_table AS t1 LEFT JOIN second_table AS t2 
    ON t2.code IN (t1.f_name, t1.l_name, t1.a_name) 
    LEFT JOIN second_table AS t3 ON FIND_IN_SET(t3.code,t1.vehicles) > 0 OR FIND_IN_SET(t3.code,t1.homes) > 0 
GROUP BY 
    t1.id, 
    t1.name

任何帮助谢谢。小提琴是here

不知道我在下面。你能分享一些样本数据和你试图得到的结果吗？ – Mureinik 2014-11-24 07:38:53

我不知道你在做什么 – Strawberry 2014-11-24 07:39:08

@Strawberry我在first_table列的home中选择连接列时出现问题，而车辆已经连接了来自第二个表的连接值，现在我想从second_table获取相关名称。 – jones 2014-11-24 08:22:57

答

试试这个

SELECT 
    t1.id, 
    t1.name, 
    CASE WHEN t2.code = t1.f_name THEN t2.name END AS name2, 
    CASE WHEN t2.code = t1.l_name THEN t2.name END AS name3, 
    CASE WHEN t2.code = t1.a_name THEN t2.name END AS name4, 
    CASE WHEN FIND_IN_SET(t3.code,t1.vehicles) > 0 THEN GROUP_CONCAT(DISTINCT(t3.name END)) AS car_owned) 
    CASE WHEN FIND_IN_SET(t3.code,t1.homes) > 0 THEN GROUP_CONCAT(DISTINCT(t3.name)) END AS home_owned) 
FROM 
    first_table AS t1 LEFT JOIN second_table AS t2 
    ON t2.code IN (t1.f_name, t1.l_name, t1.a_name) 
    LEFT JOIN second_table AS t3 ON FIND_IN_SET(t3.code,t1.vehicles) > 0 OR FIND_IN_SET(t3.code,t1.homes) > 0 
GROUP BY 
    t1.id, 
    t1.name

小提琴是here

如何在MAX中使用GROUP_CONCAT（CASE WHEN ...）？

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