sql - 合并两个表

Question

假设这 3 个表:

船舶:

    ID                   
--------------------

    1                           
    2                            
    3

到达:

 shipID     Atime 
--------------------
     1       t1 
     1       t3

离开:

 shipID     Ltime
--------------------
     1       t2
     1       t4

我需要一个返回的查询:

  shipID   Atime   Ltime
------------------------------
    1       t1       null
    1      null       t2
    1       t3       null
    1      null       t4

其中 t1>t2>t3>t4

这个结果是可以接受的:

  shipID   Atime   Ltime
------------------------------
    1       t1       null
    1       t3       null
    1      null       t2
    1      null       t4

Answer 1

尝试:

SELECT shipID, atime, null ltime from arrive
UNION ALL 
SELECT shipID, null atime, ltime from `leave`
order by coalesce(atime,ltime)

SQLFiddle here .