Question

SELECT user.id, CONCAT(lastname, firstname), year, month, date FROM user
LEFT JOIN adoption ON user.id = adoption.adopter
GROUP BY user.id

id  CONCAT(lastname, firstname) year    month   date
16  Mr.A                        2016    6       25
17  Mr.B                        2016    6       18
18  Mr.C                        NULL    NULL    NULL
19  Mr.D                        NULL    NULL    NULL

//after, I add this, should return Mr.A, C, D
HAVING SUM(CONCAT(year,month,date)= 2016618 ) = 0

我有一个查询LEFT JOIN两个表用户信息表＆amp;他们的日程表

我试图找出2016618上没有时间表的人

我使用了HAVING SUM，但它返回0行

有谁知道问题在哪里？

Answer 1

我在我的本地服务器上尝试并且@Jhecht是对的，CONCAT返回字符串，你必须在2016618上添加引用

所以你的代码必须是

 SELECT user.id, CONCAT(lastname, firstname), year, month, date FROM user
LEFT JOIN adoption ON user.id = adoption.adopter
GROUP BY user.id
HAVING SUM(CONCAT(year,month,date) = '2016618') = 0

Answer 2

我只是尝试一下你的结果，也许对你有帮助。

CREATE TABLE Table1
    (`id` int, `name` varchar(4), `year` varchar(4), `month` varchar(4), `date` varchar(4))
;

INSERT INTO Table1
    (`id`, `name`, `year`, `month`, `date`)
VALUES
    (16, 'Mr.A', '2016', '6', '25'),
    (17, 'Mr.B', '2016', '6', '18'),
    (18, 'Mr.C', NULL, NULL, NULL),
    (19, 'Mr.D', NULL, NULL, NULL)
;

SELECT * FROM Table1
GROUP BY id
HAVING SUM(if(CONCAT(year,month,date) = 2016618, 1, 0)) = 0

结果：

| id | name | year | month | date | 
+----+------+------+-------+------+
| 16 | Mr.A | 2016 | 6     | 25   | 
| 18 | Mr.C | null | null  | null | 
| 19 | Mr.D | null | null  | null |

Mysql有sum = 0返回0行

2 个答案: