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POMySql correlated subquery count across tables
 

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    <p>I have 3 tables that are related with the fields below:</p> <pre><code>forums topics posts f_id ---- f_id t_id ---- t_id p_id </code></pre> <p>For a given <code>f_id</code> I'm trying to 2 different counts in 1 query:</p> <ol> <li>the total numbers of <code>t_id</code> (topics) </li> <li>the total numbers of <code>p_id</code> (posts)</li> </ol> <p>for example <code>f_id=78</code> should simply result to</p> <pre><code>tc | pc --------- 4 | 3 </code></pre> <p>Meaning there are 4 topics and a total of 3 post to those topics, all in that forum. But when I use this simple query (which is after hours of trying and research my best attempt):</p> <pre><code>SELECT ( SELECT COUNT( t_id ) FROM topics WHERE f_id = '78' ) AS tc, ( SELECT COUNT( p_id ) FROM posts WHERE posts.t_id = topics.t_id ) AS pc FROM topics WHERE topics.f_id = '78' </code></pre> <p>But this only results to a count for each row in topics that matches the <code>f_id</code> like this:</p> <pre><code>tc | pc --------- 4 | 0 4 | 1 4 | 2 4 | 0 </code></pre> <p>and not a total count. I'm genuinely stuck here, even though I was pretty sure this was not a hard thing to achieve. Thanks!</p> <hr> <h2>Edit: as requested a bit of sample data:</h2> <p><strong>forums</strong></p> <pre><code>f_id t_name ... --------------------- 78 Test ... 33 Something ... </code></pre> <p><strong>topics</strong></p> <pre><code>f_id t_id t_date ... ---------------------------- 78 28 2011-07-14 ... 78 53 2011-07-14 ... 78 54 2011-07-14 ... 78 56 2011-07-14 ... 33 57 2011-07-14 ... </code></pre> <p><strong>posts</strong></p> <pre><code>t_id p_id p_date ... --------------------------- 54 2 2011-07-14 ... 54 4 2011-07-14 ... 53 5 2011-07-14 ... </code></pre>
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