從表中添加兩列具有相同的結構

Question

我有兩個表如下： -

  Table 1      Table 2 
     date  value    date  value 
     1120101 v11    1120102 v21 
     1120202 v12    1120303 v22 
     1120203 v13    1120104 v23 

什麼是SQL查詢來獲取以下輸出

 date   value 
     1120101  (v11) 
     1120102  (v12+v21) 
     1120103  (v13+v22) 
     1120104  (v23) 

我累了下面的查詢，但未能獲得所需的輸出

select table1.date, 
     table2.date, 
     table1.delta+table2.delta as delta 
from table1, 
    table2 
where table1.date=table2.date; 

在此先感謝。

Answer 1

SELECT date, SUM(value) 
FROM 
(
    SELECT date, value FROM table1 
    UNION ALL 
    SELECT date, value FROM table2 
) a 
GROUP BY date 

• SQLFiddle Demo (data is different but idea is the same)

Answer 2

與子查詢和工會發揮：

SELECT 
    c.date, 
    COALESCE(a.value, 0) + COALESCE(z.value,0) 
FROM (
    SELECT 
     date 
    FROM table1 
    UNION 
     SELECT date 
    FROM table2 
) AS c 
LEFT OUTER JOIN table1 a 
    ON a.date = c.date 
LEFT OUTER JOIN table2 z 
    ON z.date = c.date