從兩個表中查看同樣排序的表的用戶ID

Question

因爲我不太瞭解更復雜的SQL SELECT語句，我想這裏只是問這裏，因爲很難找到正確的主題。

我誰擁有酷似

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

相同的結構現在我想要一個SELECT來算一個特定ID的entrys兩個表中兩個表。

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

所以我認爲如果我使用一個SELECT而不是一個SELECT，數據庫性能會好很多。爲幫助了

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

感謝你能做到這一點，如：

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

另一種方法是：

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 

Answer 3

如果你想單獨計數單排，你可以使用子查詢

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