Question

我的查询应计算日期列中的日期：

将来出现日期＆＃39;没有。即将到来的＆＃39;
过去90天内发生的日期＆＃39; no。目前＆＃39;
发生超过90天的日期＆＃39;否。较旧的＆＃39;

我的查询如下：

select u.user_id, count(m.theater_release_date < CURDATE()) as 'no. upcoming',
count(m.theater_release_date BETWEEN CURDATE() - INTERVAL 90 DAY AND CURDATE()) as 'no.
currently', count(m.theater_release_date < CURDATE() - INTERVAL 90 DAY) as 'no. older'
from users u join movie m on m.movie_id = u.movie_id
group by u.user_id;

我在日期列中找回相同的数字，这显然表明我的查询没用。

 ---------+--------------+-----------------+------------+
| user_id | no. upcoming | no. currently   | no. older  |
+---------+--------------+-----------------+------------+
|       1 |          197 |             197 |        197 |
|    1929 |           11 |              11 |         11 |
|    2161 |           18 |              18 |         18 |
|    4385 |           10 |              10 |         10 |
|    4897 |            3 |               3 |          3 |
|    5737 |            6 |               6 |          6 |
|    6177 |            4 |               4 |          4 |
|    6289 |           12 |              12 |         12 |

感谢Fabricator，你的查询带回了与我非常相似的结果，现在只有中间列全部为0。

+---------+--------------+---------------+-----------+
| user_id | no. upcoming | no. currently | no. older |
+---------+--------------+---------------+-----------+
|       1 |          197 |             0 |       197 | 
|    1929 |           11 |             0 |        11 |
|    2161 |           18 |             0 |        18 |
|    4385 |           10 |             0 |        10 |
|    4897 |            3 |             0 |         3 |
|    5737 |            6 |             0 |         6 |
|    6177 |            4 |             0 |         4 |
|    6289 |           12 |             0 |        12 |
|    7353 |            6 |             0 |         6 |
|    7417 |            1 |             0 |         1 |
|    7465 |           11 |             0 |        11 |

Answer 1

MySQL将布尔值视为整数，其中true为1，false为0.因此，您只需将count()替换为sum()：

select u.user_id, sum(m.theater_release_date < CURDATE()) as `no. upcoming`,
       sum(m.theater_release_date BETWEEN CURDATE() - INTERVAL 90 DAY AND CURDATE()) as `no. currently`,
       sum(m.theater_release_date < CURDATE() - INTERVAL 90 DAY) as `no. older`
from users u join
     movie m
     on m.movie_id = u.movie_id
group by u.user_id;

注意：您应该仅对字符串和日期常量使用单引号。使用反引号（在MySQL中）来转义列别名。

Answer 2

MySQL也会计算错误值，而是使用sum(if(condition,1,0))，如下所示：

select u.user_id, sum(if(m.theater_release_date < CURDATE(),1,0)) as 'no. upcoming',
sum(if(m.theater_release_date BETWEEN CURDATE() - INTERVAL 90 DAY AND CURDATE(),1,0)) as 'no.
currently', sum(if(m.theater_release_date < CURDATE() - INTERVAL 90 DAY,1,0)) as 'no. older'
from users u join movie m on m.movie_id = u.movie_id
group by u.user_id;

需要计算列中的某个日期值

2 个答案: