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POMySQL - Join a table twice with a main table
 

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    <p>I'm not sure if this can be done. But I just wanted to check with the experts out here. </p> <p>My case is: I have a table tbl_campaign which basically stores a campaigns which has a one to many relation with a table called tbl_campaign_user where the users that were selected during the campaign are stored along with the campaign id (tbl_campagin_user.cu_campaign_id = tbl_campaign.campaign_id ).</p> <p>The second table (tbl_campaign_user) has a status field which is either 0 / 1 denoting unsent/sent. I wanted to write a single sql query which would read the campaign data as well as the number of sent and unsent campaign users (which is why I'm joining twice on the second table). I tried this below, but I get the same number of count as sent and unsent. </p> <pre><code>SELECT `tbl_campaign`.*, COUNT(sent.cu_id) as numsent, COUNT(unsent.cu_id) as num_unsent FROM (`tbl_campaign`) LEFT JOIN tbl_campaign_user as sent on (sent.cu_campaign_id = tbl_campaign.campaign_id and sent.cu_status='1') LEFT JOIN tbl_campaign_user as unsent on (unsent.cu_campaign_id = tbl_campaign.campaign_id and unsent.cu_status='0') WHERE `tbl_campaign`.`campaign_id` = '19' </code></pre> <hr> <p>I tried debugging by breaking the query into two parts: =></p> <pre><code>SELECT `tbl_campaign`.*, COUNT(unsent.cu_id) as num_unsent FROM (`tbl_campaign`) Left join tbl_campaign_user as unsent on (unsent.cu_campaign_id = tbl_campaign.campaign_id and unsent.cu_status='0') WHERE `tbl_campaign`.`campaign_id` = '19' </code></pre> <hr> <p>The above works exactly as wanted. And so does the one below:</p> <p>=></p> <pre><code>SELECT `tbl_campaign`.*, COUNT(sent.cu_id) as numsent FROM (`tbl_campaign`) Left join tbl_campaign_user as sent on (sent.cu_campaign_id = tbl_campaign.campaign_id and sent.cu_status='1') WHERE `tbl_campaign`.`campaign_id` = '19' </code></pre> <hr> <p>I am not sure what I've been doing wrong while merging the two. I know I don't know much about joins so possibly a conceptual error? Please could anyone help me?</p> <p>Thx in advance!</p>
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