从mysql“count（）”返回0的计数

Question

I have the below query running on mysql

SELECT DATE(field) AS day, COUNT( * ) AS totalSessions
FROM table
GROUP BY DATE(field) 
ORDER BY field DESC 
LIMIT 7

It returns

day        |   totalSessions
2013-12-17 |   5
2013-12-15 |   1

What would I need to change on my query so that I would get the results

day        |  totalSessions
2013-12-17 |  5
2013-12-16 |  0
2013-12-15 |  1
2013-12-14 |  0
2013-12-13 |  0
2013-12-12 |  0
2013-12-11 |  0

Answer 1

You may need to store (somewhere) the dates you want to return. I think a stored procedure can help you:

delimiter $$
create procedure getStuff(d0 date, d1 date)
begin
    declare d date;
    drop table if exists temp_dates;
    create temporary table temp_dates (
         d date not null primary key
    );
    set d = d0;
    while d <= d1 do
        insert into temp_dates values (d);
        set d = date_add(d, interval +1 day);
    end while;
    select 
        a.d as day,
        count(b.field) as totalSessions
    from
        temp_dates as a
        left join yourTable as b on a.d = b.dateField -- Assuming "dateField" holds the date
    group by
        a.d;
end $$
delimiter ;

Hope this helps

Answer 2

Not the best looking solution but worth a shot:

SELECT 
    FAKE.dt, 
    COUNT(YT.id) AS totalSessions 
FROM (
    SELECT DATE(NOW()) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 1 DAY)) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 2 DAY)) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 3 DAY)) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 4 DAY)) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 5 DAY)) as dt
    UNION SELECT DATE(DATE_SUB(NOW(), INTERVAL 6 DAY)) as dt
) FAKE
LEFT JOIN yourtable YT ON YT.datefield = FAKE.dt
GROUP BY FAKE.dt
ORDER BY FAKE.dt DESC

So you select 7 dates backwards starting today, union the results, left join the data you need, group and order by date.