mysql - JOIN 或 UNION - 不确定哪个，也许两者都有

Question

我想合并来自两个文件的数据，但我在表达排序时遇​​到了问题。我想对第一个文件的 CREATED 日期和第二个文件的 SHARED_DATE 进行排序(如果它存在并且更大)。

    file 1 : NODE# 
    fields: CREATED, CHANGED

    file 2 : SHARE_CONTENT   
    fields:  SHARED_DATE ,  NODE# (foreign key)


select * from NODE as n left join SHARE_CONTENT as s on (s.NODE#=n.NODE#)
ORDER BY [higher of n.CREATED  and s.SHARED_DATE]

Answer 1

按上次日期排序

SELECT n.*,s.*,
(CASE WHEN n.CREATED > s.SHARED_DATE then n.CREATED else s.SHARED_DATE end) as LastDate
FROM node as n LEFT JOIN share_conten as s on (s.NODE#=n.NODE#)
ORDER BY LastDate DESC