MySQL查询，COUNT和SUM（具有两个联接表）

Question

I need a little help with a MySQL query.

I have two tables one table is a list of backlinks with a is_homepage (bool) flag. The second table is a list of the domains for all of the backlinks , a was link_found (bool) flag, and a url_count column which is the number of rows in the backlinks table that are associated with each domain.

Note that the domain_id column is the foreign key to the domain table id column. Heres some sample data.

backlinks

id    domain_id    is_homepage    page_href
1     1            1              http://ablog.wordpress.com/
2     1            0              http://ablog.wordpress.com/contact/
3     1            0              http://ablog.wordpress.com/archives/
4     2            1              http://www.somewhere.org/
5     2            0              http://www.somewhere.org/page=3
6     3            1              http://www.great-fun-site.com/
7     3            0              http://www.great-fun-site.com/index.html
8     4            0              http://red.blgspot.com/page=7
9     4            0              http://blue.blgspot.com/page=9

domains

id    url_count    link_found    domain_name
1     3            1             wordpress.com
2     2            0             somewhere.org
3     2            1             great-fun-site.com
4     2            1             blgspot.com

The results Im looking to get from the above data would be: count = 2, total = 5 .

Im trying to get the count of rows from the domains table (count) and then the sum of the url_count (total) from the domains table WHERE link_found is 1 and where one of the links in the backlink table is_homepage is 1.

Here's the query I'm trying to work with.

SELECT SUM(1) AS count, SUM(`url_count`) total
FROM `domains` AS domain 
LEFT JOIN `backlinks` AS link ON link.domain_id = domain.id 
WHERE domain.id IN (
        SELECT DISTINCT(bl.domain_id)
        FROM `backlinks` AS bl
        WHERE bl.tablekey_id = 11
        AND bl.is_homepage = 1
)
AND domain.link_found = 1
AND link.is_homepage = 1
GROUP BY `domain`.`id`

The problem with this query is that it returns a row for each entry in the domains table. I think I might need one more sub query to add up the returned results but I'm not sure if that's correct. Does anyone see what I'm doing wrong? Thank you!

---

EDIT:

The problem I'm having is that if there are more than one homepage in the back-links table then its counted multiple times. I need to only count each domain once.

Answer 1

Well, you shouldn't have to do a group by as you are not selecting anything other than aggregated fields. I'm no mysql expert, but this should work:

SELECT count(d.id) as count, sum(d.url_count) as total from domains as d
inner join backlinks as b 
on b.domain_id = d.id 
 Where d.Link_found = 1  and b. is_homepage = 1

Answer 2

The reason you're getting a row for each entry in the domains table is that you're grouping by domain.id . If you want grand totals only, just leave off the GROUP BY piece.

I think a fairly simple query will do the trick:

SELECT COUNT(*), SUM(domains.URL_Count)
FROM domains
WHERE domains.link_found = 1 AND domains.id IN (
  SELECT domain_id FROM backlinks WHERE is_homepage = 1)

There's a working SQLFiddle here .

Answer 3

Thanks for the help. Sorry it was so hard to explain I need a MySQL fiddle :)

If anyones interested heres what I ened up with:

SELECT SUM(1) AS count, SUM(total) AS total
FROM
(
SELECT SUM(`url_count`) total
FROM `domains` AS domain 
LEFT JOIN `backlinks` AS link ON link.domain_id = domain.id 
WHERE domain.id IN (
        SELECT DISTINCT(bl.domain_id)
        FROM `backlinks` AS bl
        WHERE bl.tablekey_id = 11
        AND bl.is_homepage = 1
)
AND domain.link_found = 1
AND link.is_homepage = 1
GROUP BY `domain`.`id`
) AS result