mySQL查询连接五个表

Question

I have the following five tables (some fields omitted for brevity)

(campaign)
campaign_id
===========
campaign_name
campaign_description


(ad_group)
campaign_id
===========
group_id
===========
group_name


(used_ad)
campaign_id
===========
group_id
===========
ad_id
===========


(billboard_group)
campaign_id
===========
group_id
===========
group_name


(used_billboard)
campaign_id
==============
group_id
==============
billboard_code
==============

So a "campaign" is made up of 1) an "ad_group", and 2) a "billboard_group". The ad_group contains many ads (stored in the "used_ad" group), and the billboard_group contains many billboards (stored in the "used_billboard" group).

I want to run a query that will return all of the campaigns, and list the total number of ads and billboards that are related to that campaign. I've been able to do this for ad_group only, but not ad_group AND billboard_group.

For example, this query:

SELECT campaign.*, COUNT(used_ad.ad_id) AS used_ads
FROM campaign
LEFT JOIN ad_group 
  ON campaign.campaign_id = ad_group.campaign_id
LEFT JOIN used_ad
  ON ad_group.group_id = used_ad.group_id
  AND used_ad.campaign_id = campaign.campaign_id
GROUP BY campaign.campaign_id

Gives a listing like this:

campaign_id     campaign_name     campaign_description    used_ads
1               Test campaign     Testing                 4
2               Second campaign   Second                  0

But what I'm after is:

campaign_id     campaign_name     campaign_description    used_ads    used_billboards
1               Test campaign     Testing                 4           5
2               Second campaign   Second                  0           3

Only I can't seem to figure out how to include counts from BOTH used_ad and used_billboard. I'd be grateful for any help.

Answer 1

To avoid Cartesian multiplications, I'd group and count used_ad and used_billboard separately and only then join them:

SELECT campaign.*, ag.used_ads_count, bg.used_billboards_count
FROM campaign c
LEFT JOIN  (SELECT    campaign_id, COUNT(*) AS used_ads_count
            FROM      ad_group ag
            LEFT JOIN used_ad ua ON ag.group_id = ua.group_id
            GROUP BY  campaign_id) ac ON c.campaign_id = ac.campaign_id
LEFT JOIN  (SELECT    campaign_id, COUNT(*) AS used_billboards_count
            FROM      billboard_group bg
            LEFT JOIN used_billboard ub ON bg.group_id = ub.group_id
            GROUP BY  campaign_id) bc ON c.campaign_id = bc.campaign_id

Answer 2

Something like this might work if billboard_code is unique:

SELECT
  c.campaign_id, c.campaign_name, 
  COUNT(DISTINCT u.ad_id) AS used_ads,
  COUNT(DISTINCT b.billboard_code) AS used_billboards
FROM
campaign c
LEFT JOIN ad_group a ON c.campaign_id = a.campaign_id
LEFT JOIN used_ad u ON a.group_id = u.group_id
  AND c.campaign_id = u.campaign_id
LEFT JOIN used_billboard b ON c.campaign_id = b.campaign_id
  AND b.group_id = a.group_id
GROUP BY c.campaign_id

Answer 3

SELECT campaign.*, COUNT(used_ad.ad_id) AS used_ads, COUNT(used_billboard.billboard_code) as used_billboards
FROM campaign
LEFT JOIN ad_group 
  ON campaign.campaign_id = ad_group.campaign_id
LEFT JOIN billboard_group
  ON campaign.campaign_id = billboard_group.campaign_id
LEFT JOIN used_ad
  ON ad_group.group_id = used_ad.group_id
  AND used_ad.campaign_id = campaign.campaign_id
LEFT JOIN used_billboard
  ON billboard_group.group_id = used_billboard.group_id
  AND used_billboard.campaign_id = campaign.campaign_id
GROUP BY campaign.campaign_id