SQL：按两个不同的查询分组

Question

My table looks like that:

id    sex    mailsent_number    click    click_time
1466  female       1             1       2017-08-14 10:01:28   
1467  female       1             1       2017-08-14 10:45:28
1468  female       1             NULL
1469  male         1             1       2017-08-14 10:11:28
1470  male         1             NULL
1471  male         0             NULL

The following query gets me basically what I want:

select sex, 
count(mailsent_number) - count(click) NoClick, 
count(click) Click
from table group by sex;

A list with how many of each sex clicked and how many didn't click. The ones who never got an email are not counted.

Now I would like to filter the clicks by click_time. So I would like to know how many of each sex clicked BEFORE 2017-08-14 10:30 If I do this:

select sex,
count(mailsent_number) - count(click) NoClick,
count(click) Click
from table where (click_time < '2017-08-14 10:30' or click_time is null) group by sex;

Then the amount of clicks is still correct, but the amount of "no clicks" is wrong, as the one who clicked after 10:30 is not counted at all, but should be counted as "no click".

I don't know how I could get that result in one Query.

I tried with subqueries to just find out how many people got the email in an individual query, but then the group by doesn't work anymore.

Any help on that would be very appreciated.

Answer 1

I assume the logic you want is a where clause:

select sex, count(mailsent_number) - count(click) as NoClick,
       count(click) as Click
from table
where click_time < '2017-08-14 10:30' or click_time is null
group by sex ;

The reason your query seems to work is because MySQL treats sex and click_time < '2017-08-14 10:30' or click_time is null as a boolean expression, which evaluates to true or false. This then produces two rows, but there is not one for each value of sex .