mysql - 如何计算所有COUNT的总和？

我是mysql的新手。

我有一个查询要从不同的表中获取计数，它工作正常。但是，现在我想将所有3个查询COUNT合并为1，例如SUM（COUNT1，COUNT2，COUNT3）

select COUNT(*) as count1, 0 as count2, 0 as count3 from table1
UNION ALL
select 0 as count1, COUNT(*) as count2, 0 as count3 from table2
UNION ALL
select 0 as count1, 0 as count2, COUNT(*) as count3 from table3

例如。 count1 = 10，count2 = 20和count3 = 15

然后，我想求和= 45

最佳答案

您可以将UNION放在子查询中，然后将SUM()计数。但是，无需在每个联合查询中将它们放在单独的列中。

SELECT SUM(count) AS total
FROM (
    SELECT COUNT(*) AS count FROM table1
    UNION ALL
    SELECT COUNT(*) AS count FROM table2
    UNION ALL
    SELECT COUNT(*) AS count FROM table3
) AS subquery

关于mysql - 如何计算所有COUNT的总和？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47975437/