SELECT (SELECT COUNT(*) FROM table1) + (SELECT COUNT(*) FROM table2) FROM dual;

其他略有不同的方法:

with t1_count as (select count(*) c1 from t1),
     t2_count as (select count(*) c2 from t2)
select c1,
       c2
from   t1_count,
       t2_count
/

select c1,
       c2
from   (select count(*) c1 from t1) t1_count,
       (select count(*) c2 from t2) t2_count
/

作为附加信息，要在SQL Server中完成同样的事情，您只需要删除查询的“FROM dual”部分。

选择 (select count() from tab1 where field like 'value') + (select count() from tab2 where field like 'value') 数

select (select count(*) from tab1) count_1, (select count(*) from tab2) count_2 from dual;

我很快想到了:

Select (select count(*) from Table1) as Count1, (select count(*) from Table2) as Count2

注意:我在SQL Server中测试了这个，所以从Dual是不必要的(因此存在差异)。