每个表(表1和表2)具有其自己的DATETIME字段.
我正在尝试捕获两个表的ID,并按其DATETIME字段对其进行排序.
例:
Table 1 Table 2
------------ -------------
id | datetime1 id | table1id | datetime2
------------------------ -----------------------
1 | 2014-09-21 20:31:26 1 | 2 | 2014-09-21 20:31:29
2 | 2014-09-21 20:31:27 2 | 3 | 2014-09-21 20:31:30
3 | 2014-09-21 20:31:28
Table 3
------------
id | user
------------------------
2 | phil
3 | nathalie
SELECT *
FROM (
SELECT
1 AS selection,
table1.id, table1.datetime1,
table2.datetime2
table3.user
FROM Table1
LEFT OUTER JOIN table2
ON table1.id = table2.table1id
LEFT OUTER JOIN table3
ON table1.id = table3.id
UNION ALL
SELECT
2 AS selection,
table1.id, table1.datetime1,
table2.datetime2
table3.user
FROM Table1
INNER JOIN table2
ON table1.id = table2.table1id
INNER JOIN table3
ON table1.id = table3.id
) AS query
ORDER BY table1.datetime1 DESC, table2.datetime2 DESC
所需数据:
从表2 id:2,1,
从表1 id:3,2,1
因此:2、1、3、2、1
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解决方法:
您真正需要做的是更仔细地考虑架构.考虑将日期时间列命名为相同的名称,然后运行如下查询-http://sqlfiddle.com/#!2/a3b4c/7/0
SELECT selection, id, datetimefoo, user FROM (
SELECT
1 AS selection,
table1.id, table1.datetimefoo,
table3.user
FROM table1
LEFT OUTER JOIN table2
ON table1.id = table2.table1id
LEFT OUTER JOIN table3
ON table1.id = table3.id
UNION
SELECT
2 AS selection,
table1.id, table1.datetimefoo,
table3.user
FROM table1
INNER JOIN table2
ON table1.id = table2.table1id
INNER JOIN table3
ON table1.id = table3.id
) AS T2
ORDER BY datetimefoo DESC
在sql提琴中,这会产生与您要查找的结果更接近的结果.我仍然不确定为什么您需要在第二个查询上使用INNER JOINS-在这里您不需要做什么.
这是另一种方法,不需要更改列名,但需要可排序列的别名-http://sqlfiddle.com/#!2/ec4bc/3/0
SELECT * FROM (
SELECT
1 AS selection,
table1.id, table1.datetimefoo AS sort_date, -- alias on first table's date
table2.datetimebar,
table3.user
FROM table1
LEFT OUTER JOIN table2
ON table1.id = table2.table1id
LEFT OUTER JOIN table3
ON table1.id = table3.id
UNION
SELECT
2 AS selection,
table1.id, table1.datetimefoo,
table2.datetimebar AS sort_date, -- alias on second table's date
table3.user
FROM table1
INNER JOIN table2
ON table1.id = table2.table1id
INNER JOIN table3
ON table1.id = table3.id
) AS T2
ORDER BY sort_date DESC