mysql - 如何对多个表中存在的相同列求和并将结果显示为一个

Question

我有超过 4 个具有相同列的表，我只想对列求和并将结果显示为每列一个。我的桌子是：

表格1

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

Table2 

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

Table3. 

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

预期结果：

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函数也有 where 子句。

标签： mysqlsum

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