从两个表中计算uid，这些表按表名查找相同的排序

Question

因为我想在这里提出更复杂的SQL SELECT语句，因为我很难在主题上找到正确的东西。

我有两张表具有完全相同的结构，如

TABLE A (id (INT(11)), time (VARCHAR(10));)
TABLE B (id (INT(11)), time (VARCHAR(10));)

现在我想要一个SELECT来计算两个表中特定id的编码。

SELECT COUNT(*) FROM TABLE A WHERE id = '1';
SELECT COUNT(*) FROM TABLE B WHERE id = '1';

所以我认为如果我使用一个SELECT而不是一个SELECT，那对数据库性能会好得多。

感谢您提供帮助

Answer 1

SELECT COUNT(*) as count, 'tableA' as table_name FROM TABLEA WHERE id = '1'
union all
SELECT COUNT(*), 'tableB' FROM TABLEB WHERE id = '1'

Answer 2

如果您想在单行中使用单独的计数，则可以使用子查询

SELECT 
    (SELECT COUNT(*) FROM TABLE A WHERE id = '1') a_count,
    (SELECT COUNT(*) FROM TABLE B WHERE id = '1') b_count;

Answer 3

你可以这样做：

select count(*) 
from (
    select id from t1 where id = 1
    union all
    select id from t2 where id = 1
) as t

另一种选择是：

select sum(cnt) 
from (
    select count(*) as cnt from t1 where id = 1
    union all
    select count(*) as cnt from t2 where id = 1
) as t