MYSQL将两个表与两个列进行比较

Question

I have two tables 1)users(id,registerdate) 2)user_answer(userid,answer,updated_date)

I want the count of zero usage per day. How many users are registering but not answering per day. Results will be like this:

Date        registedCount   notAnsweredCount

15-09-02    20              10
15-09-01    20              10
15-08-31    12              4

Thanks in advance.

Answer 1

Using a SUM of the result of an IF statement:-

SELECT date_range.aDay, 
        COUNT(DISTINCT users.id) AS registedCount, 
        SUM(IF(users.id IS NOT NULL AND user_answer.userid IS NULL, 1, 0)) AS notAnsweredCount
FROM
(
    SELECT DATE_ADD('2015-09-01', INTERVAL units.aCnt + tens.aCnt * 10 DAY) AS aDay
    FROM
    (
        SELECT 0 AS aCnt UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9
    ) units
    CROSS JOIN
    (
        SELECT 0 AS aCnt UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9 
    ) tens
) date_range
LEFT OUTER JOIN users
ON date_range.aDay = users.registerdate
LEFT OUTER JOIN user_answer
ON users.id = user_answer.userid
GROUP BY date_range.aDay

This is getting a range of numbers to add to a date, to give a range of dates (in this case 100 days from 1st September inclusive). This is then LEFT OUTER JOINed against users matching on the register date, and then that is LEFT OUTER JOINed against user_answer. It does a count of distinct user.id to get the number of people who registered on each date, and it sums up where the userids from user_answer is NULL (ie, haven't answered any question).

EDIT - if you do not care about having gaps in the returned data for days where no user registered, and want a list of all days where at least 1 person registered this this simple query will do the job:-

SELECT users.registerdate, 
        COUNT(DISTINCT users.id) AS registedCount, 
        SUM(IF(user_answer.userid IS NULL, 1, 0)) AS notAnsweredCount
FROM users
LEFT OUTER JOIN user_answer
ON users.id = user_answer.userid
GROUP BY users.registerdate

Answer 2

Check the following query, it should get you the desired results

SELECT results.date, 
    SUM(results.answered) as answered,
    COUNT(results.userid)-SUM(results.answered) as notanswered
FROM
(SELECT @id:= u.id as userid, @regdate:= u.regdate as date,
   (CASE WHEN EXISTS (SELECT 1 FROM user_answer WHERE updated_date = @regdate AND userid = @id)
    THEN 1 ELSE 0 END) AS answered
FROM users u) AS results
GROUP BY results.date