在MYSQL中查看3个表

我在mysql中有3个表

table 1
date        name   total recieve
2013-05-09  "aa"    20    15
2013-05-09  "bb"    10    17

table 2
name    tree
"bb"     "a1"
"aa"     "a2"

table 3
date          tree      users
2013-05-09   "a1SI"      19
2013-05-09   "a1NO"      24
2013-05-09   "a2SI"      39
2013-05-09   "a2NO"      22

我需要一个带树表的视图

这是我需要的观点：

date         name   tree   total    recieve    userSI    userNO  
2013-05-09   "aa"   "a2"    20        15        39         22
2013-05-09   "bb"   "a1"    10        17        19         24

我有一半的疑问

SELECT t1.`date` , t1.`name` , t2.`tree` , t1.`total` , t1.`recieve`,
FROM  `table1` t1
INNER JOIN  `table2` t2 ON t1.`name` = t2.`name` 
ORDER BY  `t1`.`date` DESC

---

但我不知道如何使用三个表查看，其他问题是树的记录，因为我有树“a1”、“a1Si”和“a2NO”在视图中，我需要关联3列

，您应该能够使用以下内容将

t2.tree

上的

表3

与

t3.tree

的左两个字符连接起来：

SELECT t1.`date` , t1.`name` , t2.`tree` , t1.`total` , t1.`recieve`,
  max(case when right(t3.tree, 2) = 'SI' then t3.users end) usersSI,
  max(case when right(t3.tree, 2) = 'NO' then t3.users end) usersNO
FROM  `table1` t1
INNER JOIN  `table2` t2 
  ON t1.`name` = t2.`name` 
INNER JOIN `table3` t3
  on t2.tree = left(t3.tree, 2)
group by t1.`date` , t1.`name` , t2.`tree` , t1.`total` , t1.`recieve`
ORDER BY  `t1`.`date` DESC;

看

这也可以使用表3中的多个联接来完成：

SELECT t1.`date` , t1.`name` , t2.`tree` , t1.`total` , t1.`recieve`,
  t3SI.users usersSI,
  t3NO.users usersNO
FROM  `table1` t1
INNER JOIN  `table2` t2 
  ON t1.`name` = t2.`name` 
LEFT JOIN `table3` t3SI
  on t2.tree = left(t3SI.tree, 2)
  and right(t3SI.tree, 2) = 'SI'
LEFT JOIN `table3` t3NO
  on t2.tree = left(t3NO.tree, 2)
  and right(t3NO.tree, 2) = 'NO'
ORDER BY  `t1`.`date` DESC;

看。您会注意到，我更改了最后两个联接，以使用

左联接

，如果不存在与

SI

或

NO

匹配的树，则您将返回数据。如果您知道将有匹配的数据，那么可以使用内部联接

如果树名较长，则可以在JOIN中实现LIKE子句：

SELECT t1.`date` , t1.`name` , t2.`tree` , t1.`total` , t1.`recieve`,
  t3SI.users usersSI,
  t3NO.users usersNO
FROM  `table1` t1
INNER JOIN  `table2` t2 
  ON t1.`name` = t2.`name` 
LEFT JOIN `table3` t3SI
  on t3SI.tree like concat(t2.tree, '%')
  and right(t3SI.tree, 2) = 'SI'
LEFT JOIN `table3` t3NO
  on t3NO.tree like concat(t2.tree, '%')
  and right(t3NO.tree, 2) = 'NO'
ORDER BY  `t1`.`date` DESC;

---

请参见

尝试与第三个表进行两次内部联接，如下所示：

    SELECT t1.'date' , t1.'name' , t2.'tree' , t1.'total' , t1.'recieve',
      t31.users usersSI,
      t32.users usersNO
    FROM  'table1' t1
    INNER JOIN  'table2' t2 
      ON t1.'name' = t2.'name' 
    INNER JOIN 'table3' t31
      on t2.tree = left(t31.tree, 2) AND right(t31.tree, 2) = 'SI'
    INNER JOIN 'table3' t32
      on t2.tree = left(t32.tree, 2) AND right(t32.tree, 2) = 'NO'
    group by t1.'date' , t1.'name' , t2.'tree' , t1.'total' , t1.'recieve'
    ORDER BY  't1'.'date' DESC;

---

但是当我做max（case when right（t3.tree，2）=‘SI’然后t3.users end）usersSI时，max（case when right（t3.tree，2）=‘NO’然后t3.users end）usersNO。只显示一条记录，我有80条记录，其中userSI和userNO@BenitoCamelas参见我的编辑，你也可以使用多个连接来获得结果。哦，问题是当你离开（t3SI.tree，2）时，如果一棵树的aname有5个字母，而不是working@BenitoCamelas你应该在你的原始帖子中包含所有必要的细节。您也可以尝试在JOIN中使用LIKE子句。@BlueFoots为意外的否决投票（以及随后的奇怪编辑来解锁投票）感到抱歉。我一定是在没有意识到的情况下疯狂地点击了。现在投票吧！