Question

我想基本上取一个数字（total_score）并除以＆lt; =今天的（release_date）数。我肯定想在SELECT语句中进行数学运算。我尝试了这个但它似乎不起作用：

SELECT 
total_score / COUNT(release_date <= CURDATE()) as final_score
from movies
WHERE id = 12

所以说总得分是400，而且＆lt; =今天的release_dates数量是2. final_score应该是200.

我可以像这样在SELECT语句中计算吗？ COUNT(release_date <= CURDATE())

Answer 1

也许试试这个：

SELECT 
total_score / (SELECT COUNT(release_date) FROM movies where release_date <= CURDATE()) as final_score
from movies
WHERE id = 12

Answer 2

也许尝试这样的事情： -

SELECT (total_score / score_count) as final_score
FROM movies
CROSS JOIN (SELECT COUNT(*) as score_count
FROM movies
WHERE release_date <= CURDATE()) AS Sub1
WHERE id = 12

Answer 3

一个不起作用的原因是你只选择一行（其中id = 12）。您需要从表中选择两次。一次获取id为12的total_score，另一次计算CURDATE之前的行数。尝试类似：

select A.total_score / count(B.release_date) from movies as A, movies as B
   where A.id=12 and B.release_date <= CURDATE();

Answer 4

根据我的假设，Id是主键（即Movie的ID）。然后查询返回总是单行。现在到final_score取决于发布日期。该发布日期必须早于当前日期，因此以下查询足以实现您的目标，

SELECT total_score / DATEDIFF(CURDATE(), release_date) AS final_score FROM movies WHERE id = 12

MySQL：在SELECT语句中使用COUNT计算数字？

4 个答案: