Question

I have a mysql table like with the following rows:

id  |  event_type  |  occurance_date  |  ipaddress

I want to get the days, unique visits and total visits / day. This is pretty easy to do with 2 queries but I want to make only one.

So i thought
To get the days i can

SELECT DISTINCT(occurance_date) as day FROM statistics WHERE event_type = 'visit' 
ORDER BY id DESC LIMIT 14;

To get unique visits / day

SELECT COUNT(DISTINCT(ipaddress)) as unique_visits FROM statistics WHERE occurance_date = '2011-05-11';

To get all visits / day

SELECT COUNT(id) as total_visits FROM statistics WHERE occurance_date = '2011-05-11';

The problem is how can I make a single query to return me the all the days, with unique_visits and total_visits.

(2011-05-11 should be replaced by date, it’s just an example)

Any suggestion is more then welcomed.

Thanks.

Answer 1

select count(*) as total_visits, count(distinct(s1.ipaddress)) as unique_visits 
FROM statistics s1 
WHERE event_type = 'visit'
GROUP BY occurrence
ORDER BY unique_visits;

Annotated version:

First we do a SELECT count(all rows)

select count(*) as total_visits, 

Plus a count of the distinct ipaddresses

count(distinct(s1.ipaddress)) as unique_visits 

From statistics, I’ve added an alias, but that’s just out of habit. It is not needed.

FROM statistics s1

Remember you wanted only rows that had event_type ‘visit’.
You also had some information need about that, but you did not want to filter those out, you just wanted to see them as separate items in the result.
So the only filter we have is event_type.

WHERE event_type = 'visit'

We group the result by occurrence date, if you leave this line out, you will only see one line. Put it back in to see the difference.

GROUP BY occurrence

And we order the results by number of visits, except I didn’t want to rewrite count(distinct(s1.ipaddress)) so I wrote the alias unique_visits; this is allowed (and even encouraged in an order by clause.)

ORDER BY unique_visits;

Links:
Group by, never mind about this myth part, just read the description of how group by works:
http://dev.mysql.com/tech-resources/articles/debunking-group-by-myths.html
Count: http://dev.mysql.com/doc/refman/5.1/en/counting-rows.html