Question

我有一个表跟随者并且跟随计数..

想要在一个存储过程中得到两者的计数..是否可以在同一个表上有两个具有不同where条件的选择查询？

CREATE TABLE Table1
    ([val1] int, [val2] int, [val3] int, [val4] int, other int)
;

INSERT INTO Table1
    ([val1], [val2], [val3], [val4], other)
VALUES
    (1, 26, 13, 1, 1),
    (2, 13, 26, 1, 1),
(3, 10, 26, 1, 1),
(4, 26, 13, 1, 1),
(5, 14, 26, 1, 1)
;

我选择查询

(select count(*) as following_count from table1 where val2=26)

(select count(*) as follower_count from table1 where val3=26)

SQL FIDDLE LINK

Answer 1

你可以这样做：

SELECT
    SUM(CASE WHEN val2=26 THEN 1 ELSE 0 END) AS following_count,
    SUM(CASE WHEN val3=26 THEN 1 ELSE 0 END) AS follower_count
FROM
    table1

Answer 2

为什么不使用UNION ALL激活这两个语句？

请参阅：http://dev.mysql.com/doc/refman/5.1/de/union.html

SO：

SELECT COUNT(*) AS following_count FROM table1 WHERE val2=26
UNION ALL
SELECT COUNT(*) AS following_count FROM table1 WHERE val3=26

在1个查询中返回两行，包含2个数字。

在两列中执行此操作：

SELECT
  (SELECT COUNT(*) AS following_count FROM table1 WHERE val2=26) col1
  , (SELECT COUNT(*) AS following_count FROM table1 WHERE val3=26) col2

Answer 3

只需在你的陈述中添加分号......

(select count(*) as following_count from table1 where val2=26);

(select count(*) as follower_count from table1 where val3=26);

两个选择查询在同一个表上使用不同的where子句

3 个答案: