Question

$userid = 1; // got from session
select tableone.userid, tableone.name, tabletwo.action as action
from tableone
leftjoin tabletwo
where tabletwo.userid = $userid
on tableone.jailid = tabletwo.jailid

它从tableone返回all并且全部来自tabletwo，但问题是表2的列之一，即action只返回一个但是在tabletwo中有多个行符合条件（tablewo.userid = $ userid on tableone .jailid = tabletwo.jailid）。

它返回：

userid => 23
name => test title
action => 65

userid => 24
name => test title2
action => 65

我想：

userid => 23
name => test title
action => [65, 66, 67]

userid => 24
name => test title2
action => [76, 57, 34]

我该如何解决这个问题？

Answer 1

您可以将GROUP BY与GROUP_CONCAT一起使用，例如：

SELECT tableone.userid, tableone.name, GROUP_CONCAT(tabletwo.action) AS action
FROM tableone
LEFT JOIN tabletwo
ON tableone.jailid = tabletwo.jailid
WHERE tabletwo.userid = $userid
GROUP BY tableone.userid, tableone.name;

Here's GROUP_CONCAT函数的文档。

mysql - 来自两个表的多行和来自第二个表列之一的多个值

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