Question

我有三个选择语句如下，我想总结一下记录的总数。我怎么能这样做？

SELECT COUNT(*) AS Number FROM tableA where user_id = 5   //Total 5 records
SELECT COUNT(*) AS Number FROM tableB where user_id = 5   //Total 6 records
SELECT COUNT(*) AS Number FROM tableC where user_id = 5   //Total 1 records

所以返回结果将是12。

Answer 1

您可以将count(*)应用于union all：

的结果

SELECT COUNT(*)
FROM   (SELECT user_id FROM tablea
        UNION ALL
        SELECT user_id FROM tableb
        UNION ALL
        SELECT user_id FROM tablec) t
WHERE  user_id = 5

Answer 2

我认为这应该可以解决问题：

SELECT SUM(Number)
FROM (
    SELECT COUNT(*) AS Number FROM tableA where user_id = 5
    UNION ALL
    SELECT COUNT(*) AS Number FROM tableB where user_id = 5
    UNION ALL
    SELECT COUNT(*) AS Number FROM tableC where user_id = 5
)

Answer 3

select ( select count(*) from tableA where user_id = 5 )
     + ( select count(*) from tableB where user_id = 5 ) 
     + ( select count(*) from tableC where user_id = 5 ) 
     as total_rows
from dual

如何总计3个选择语句计数？

3 个答案: