sql查询两个表中满足某些条件的数据总数

Question

有两个表，现在要查询出两个表都满足条件A,B,C的数据总数

Answer 1

假设两张表分别为TAB1,TAB2:
SELECT SUM(CNT) FROM (
SELECT COUNT(1) CNT FROM TAB1 WHERE 满足条件A,B,C
UNION ALL
SELECT COUNT(1) CNT FROM TAB2 WHERE 满足条件A,B,C)

Answer 2

如果字段一样的话，可以用union all，即
select * from 表1 where A,B,C
union all
select * from 表2 where A,B,C

Answer 3

select 
(select count(*) from t1 where ...)
+
(select count(*) from t2 where ...)

Answer 4

select COUNT(字段A) from TABLE1 where A AND B AND C
union al
lselect COUNT(字段B) from TABLE2 where A AND B AND C