关于一次打印3个表的SQL查询

Question

代码:

 select count(*) AS "NR_COMEDIES" from COMEDY

 select count(*) AS "NR_DRAMAS" from DRAMA 

 select count(*) AS "NR_TRAGEDIES" from TRAGEDY

我正在尝试将所有 3 个表的计数函数打印为一张大表。

其中每个表都有自己的列，如上面命名。如何将所有 3 张 table 放在一张大 table 上？

我尝试使用 union 但不起作用。

Answer 1

也许CROSS JOIN应该适合你

SELECT A.NR_COMEDIES,
       B.NR_DRAMAS,
       C.NR_TRAGEDIES
FROM   (SELECT Count(*) AS "NR_COMEDIES"
        FROM   COMEDY) A
       CROSS JOIN (SELECT Count(*) AS "NR_DRAMAS"
                   FROM   DRAMA)B
       CROSS JOIN (SELECT Count(*) AS "NR_TRAGEDIES"
                   FROM   TRAGEDY) C 

或在所有查询之间执行笛卡尔积

SELECT A.NR_COMEDIES,
       B.NR_DRAMAS,
       C.NR_TRAGEDIES
FROM   (SELECT Count(*) AS "NR_COMEDIES"
        FROM   COMEDY) A,
       (SELECT Count(*) AS "NR_DRAMAS"
        FROM   DRAMA)B,
       (SELECT Count(*) AS "NR_TRAGEDIES"
        FROM   TRAGEDY) C