sql两个表的总和

Question

how to get a sum of two sums from two tables? 如何从两个表中得到两个总和？

SELECT (SELECT SUM(col) FROM table1) + SELECT (SUM(col) from table2)

doesn't work 不起作用

Answer 1

You are very close. 你很亲密 You just need parens around each subquery: 您只需要在每个子查询周围添加括号：

SELECT (SELECT SUM(col) FROM table1) + (SELECT SUM(col) from table2)

If either subquery could return NULL , you might prefer: 如果任何一个子查询都可以返回NULL ，则您可能更喜欢：

SELECT COALESCE(t1.s, 0) + COALESCE(t2.s)
FROM (SELECT SUM(col) as s FROM table1) t1 CROSS JOIN
     (SELECT SUM(col) as s from table2) t2;

Answer 2

Due to this link , you can do that by : 由于此链接，您可以通过以下方法实现：

SELECT T1C1 , T2C1
FROM
 ( select SUM(Col1) T1C1 FROM  T1 ) A
CROSS JOIN 
 ( select SUM(Col1) T2C1 FROM  T2 ) B

also you can visit these links: 您也可以访问以下链接：

Answer 3

select coalesce(sum(x),0) from
 (
    Select sum(a) x from tab1
    Union all
    Select sum(b) from tab2
 ) Ilv