[英]SQL SELECT only rows having MAX value of a column from two different tables
我的两个表设置如下:
表格1
+------+---------+--------------------------------------+ | id | tail | content | +------+---------+--------------------------------------+ | 1 | abc | ... | | 2 | def | ... | | 3 | ghi | ... | | 4 | def | ... | | 5 | jkl | ... | +------+-------+----------------------------------------+
表2
+------+--------+---------------------------------------+ | id | tailID | value | others | +------+--------+---------------------------------------+ | 1 | 2 | 412 | | | 2 | 3 | 215 | | | 1 | 2 | 571 | | | 1 | 4 | 123 | | +------+--------+---------------------------------------+
我喜欢将这两个表中的所有列连接到匹配的tail = tailID,但不是具有相同尾部的重复行。
对于重复的TAIL,只需要获得相同尾部的最大VALUE的单行。
我目前正在使用
SELECT table1.tail, table2.other_column FROM table1 INNER JOIN table2 on table1.id = table2.tailID WHERE table1.some_coloum = "a sepecific string" ORDER BY table2.value
但它会返回许多相同尾部的副本。
我只需要对于具有高位值tableUE 2的重复TAIL有单行。
DISTINCT与交叉申请:
SELECT DISTINCT t1.tail,
t2.other_column,
t3.[value]
FROM table1 t1
CROSS APPLY (
SELECT tailid,
MAX([value]) as [value]
FROM table2
WHERE tailid = t1.id
GROUP BY tailid
) as t3
INNER JOIN table2 t2
ON t2.tailid = t3.tailid AND t3.[value] = t2.[value]
WHERE t1.some_coloum = "a sepecific string"
然后第一组table2加入
SELECT table1.tail, table2.other_column
FROM table1
INNER JOIN (
SELECT tailID, max(value) as value
FROM table2
GROUP BY tailID
) t2g ON t2g.tailID = table1.ID
INNER JOIN table2
on t2g.tailID = table2.tailID AND t2g.value = table2.value
WHERE table1.some_coloum = "a sepecific string"
ORDER BY table2.value
如果table2
有2行或更多行具有相同的max(value)
和tailID
,则查询仍可能为table1
行返回多行。
只选择行,其中是列MAX值value
SELECT table1.tail, MAX(table2.value)
FROM
table1
INNER JOIN table2 ON table1.id = table2.tailID
WHERE table1.content = "test"
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.