Question

tableone: id | userid | date | photo | caption | visible
tabletwo: id | userid | date | text  | gender  | notes

我有两个不同列的表。我想使用单个查询从两者中选择行，我会使用日期（时间戳）和用户ID来执行此操作。是否可以将它们连接在一起？

SELECT id, photo, caption, visible
FROM `tableone`
WHERE `userid` = $user->id AND `date` = '$d'
ORDER BY date desc

SELECT id, text, gender, notes
FROM `tabletwo`
WHERE `userid` = $user->id AND `date` = '$d'
ORDER BY date desc
LIMIT 1

编辑：期望的输出：

(
    [id] => 3
    [photo] => 1
    [caption] => Sample text
    [visible] => 1
    [text] => 
    [gender] => 
    [notes] => 
)
(
    [id] => 23
    [photo] => 1
    [caption] => More sample text
    [visible] => 
    [text] => 
    [gender] => 
    [notes] => 
)
(
    [id] => 1
    [photo] => 
    [caption] => 
    [visible] => 
    [text] => Blah jaspidj
    [gender] => 2
    [notes] => Sample Text
)

Answer 1

所以你可以得到两个表行数据都有用户ID和日期像param一样？好的，必须使用JOIN将它们全部放在一行

SELECT t1.id, t1.userid, t1.date, t1.photo, t1.caption, t1.visible, t2.text, t2.gender, t2.notes
FROM tableone t1 JOIN tableone t2 ON t1.ID = t2.ID
WHERE t1.userid = "yourwantedid" AND t1.date = "yourwanteddate"

您只能在WHERE子句中使用表1，因为您将两个表连接在一起。

抱歉我的英语不好。希望这个帮助

我最近看到你的评论，可能你想使用UNION ALL子句

SELECT t1.id, t1.userid, t1.date, t1.photo, t1.caption, t1.visible
FROM tableone t1
WHERE userid = "yourwantedid" AND date = "yourwanteddate"
UNION ALL
SELECT t2.id, t2.userid, t2.date, t2.text as photo, t2.gender as caption, t2.notes as visible
FROM tabletwo t2
WHERE userid = "yourwantedid" AND date = "yourwanteddate"

您必须在列上添加别名以使用UNION ALL子句，该子句与两个选择的列名称匹配。

抱歉我的英语不好。希望这个帮助

Answer 2

您正在寻找的概念是UNION（请参阅MySql UNION reference），它将两个查询的结果组合在一起。通常，您只联合具有相同列的结果，但是您要求联合两种不同类型的查询。如果您关心的是所有结果并且您不关心空白单元格，那么这应该对您有用：

(SELECT id, photo, caption, visible, null AS text, null AS gender, null AS notes
FROM `tableone`
WHERE `userid` = $user->id AND `date` = '$d'
ORDER BY date desc)
UNION ALL
(SELECT id, null AS photo, null AS caption, null AS visible, text, gender, notes
FROM `tabletwo`
WHERE `userid` = $user->id AND `date` = '$d'
ORDER BY date desc
LIMIT 1)

（请注意，我使用了UNION ALL代替UNION，这基本上意味着“给我所有结果，包括重复”。由于此套装中无法重复，因此安全使用UNION ALL来提升效果

这个输出在逻辑上没有意义，但它应该给你上面显示的示例输出。

选择查询以连接两个表？

2 个答案: