Mysql从2个不同的表中选择并合并结果

Question

我想向您寻求有关 mysql 的帮助。我想合并两个完全不同的具有日期列的表。表格看起来像这样:

选项卡1:

NAMECOLUMN   |      DATECOLUMN
------------------------------
itemname1    |      2013-01-01
itemname2    |      2013-02-02
itemname3    |      2012-04-01

选项卡2:

OTHERCOLUMN  |      DATECOLUMN
------------------------------
xyz         |      2013-01-31
abcd        |      2013-01-02
efgh        |      2012-03-01

我希望结果按时间排序:

OTHERCOLUMN |      NAMECOLUMN      DATECOLUMN
---------------------------------------------
(null)      |      itemname1       2013-01-01
xyz         |      (null)          2013-01-31
abcd        |      (null)          2013-01-02
(null)      |      itemname2       2013-02-02
efgh        |      (null)          2012-03-01
(null)      |      itemname3       2012-04-01

谢谢你给我指路:)

Answer 1

试试这个:

SELECT *
FROM (
  SELECT NULL AS othercolumn, NAMECOLUMN, datecolumn
  FROM tab1      
  UNION
  SELECT otherColumn, NULL, dateColumn
  FROM tab2
  ) a
ORDER BY datecolumn

sqlfiddle demo

编辑:

根据您的新表3，您可以执行以下操作:

SELECT *
FROM (
  SELECT NULL as otherColumn, t1.NAMECOLUMN, t3.category,t3.type, t1.datecolumn
  FROM tab1 t1      
  INNER JOIN tab3 t3 ON t1.tab3id = t3.id
  UNION
  SELECT otherColumn, NULL,NULL,NULL, dateColumn
  FROM tab2
  ) a
ORDER BY datecolumn;

sqlfiddle demo