如何從一個查詢中排序兩個表中的不同值？

Question

我

• 表1：country，theOrderColumn1
• 表2：country，theOrderColumn2

我想加入這兩個SELECT語句DISTINCT country：

SELECT DISTINCT `country` FROM `table1` ORDER BY `theOrderColumn1` 

和

SELECT DISTINCT `country` FROM `table2` ORDER BY `theOrderColumn2` 

例子：

table1 (country, theOrderColumn1): (uk, 1), (usa, 2)
table2 (country, theOrderColumn2): (france, 1), (uk, 2)

我想這樣的結果：

france 
uk 
usa 

Answer 1

select distinct country 
from (
    select country, theOrderColumn from table1 
    union all 
    select country, theOrderColumn from table2 
) a 
order by theOrderColumn 

Answer 2

select country, theOrderColumn from (
select distinct t1.country as country, t1.theOrderColumn as theOrderColumn from table t1 
union 
select distinct t2.country as country, t2.theOrderColumn as theOrderColumn from table t2) t3 
order by theOrderColumn 

Answer 3

select a.country,a.theOrderColumn 
(
select country,theOrderColumn 
from table1 
union 
select country,theOrderColumn 
from table2 
) a 
order by a.theOrderColumn 

雖然如果OrderColumn在表1和表2中不同，您將得到重複。

Answer 4

這取決於您想要什麼以及如何將兩個表連接在一起。如果您是基於「theOrderColumn」的加盟，那麼查詢將

SELECT DISTINCT country 
FROM table1 
JOIN table2 ON table1.theOrderColumn = table2.theOrderColumn 
ORDER BY theOrderColumn 

如果要在全國的加盟（這是沒有意義的國家將是兩個表中相同），那麼你可以換加入條款中的「國家」。

此外，根據您DBMS所說的SQL方言，您的里程可能會因上述查詢而異。你能澄清你更多嗎？

Answer 5

如果要同時保留theOrderColumn1和theOrderColumn2給出的訂單，可以使用列索引指定ORDER BY列。

SELECT distinct country FROM(

    (SELECT country as c, theOrderColumn1 as d from table1 
    UNION 
    SELECT country as c, theOrderColumn2 as d from table2 
) 
    order by 2 
) 

看看在這個問題的答案：SQL Query - Using Order By in UNION