如何對多個表中存在的相同列求和並將結果顯示為一個

Question

我有4個以上具有相同列的表，我只想對這些列求和並將結果顯示為每一列。 我的桌子是：

表格1

-----------------------------------------------
| amount  |    tax1.  |    tax2.  |    gtotal |
----------------------------------------------

Table2 

-----------------------------------------------
| amount  |    tax1.  |    tax2.  |    gtotal |
----------------------------------------------

Table3. 

 -----------------------------------------------
| amount  |    tax1.  |    tax2.  |    gtotal |
----------------------------------------------

預期結果：

SELECT SUM(amount) FROM All_Tables

SELECT SUM(tax1) FROM All_Tables

SELECT SUM(tax2) FROM All_Tables

SELECT SUM(gtotal) FROM All_Tables

和SUM函數也具有where子句。

Answer 1

SELECT SUM(amount), SUM(tax1), SUM(tax2), SUM(gtotal) 
FROM (
SELECT SUM(amount), SUM(tax1), SUM(tax2), SUM(gtotal) FROM Table1
UNION ALL SELECT SUM(amount), SUM(tax1), SUM(tax2), SUM(gtotal) FROM Table2) a

Answer 2

聯盟是您想要的：

SELECT SUM(amount), SUM(tax1), SUM(tax2), SUM(amount + tax1 + tax2)
FROM(
            SELECT amount, tax1, tax2, gtotal FROM Table1 
  UNION ALL SELECT amount, tax1, tax2, gtotal FROM Table2
  UNION ALL SELECT amount, tax1, tax2, gtotal FROM Table3
)