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    <p>SQL doesn't typically allow you to reference column aliases in WHERE, GROUP BY or HAVING clauses. MySQL does support referencing column aliases in the GROUP BY and HAVING, but I stress that it will cause problems when porting such queries to other databases.</p> <p>When in doubt, use the actual column name:</p> <pre><code>SELECT t.lat AS latitude FROM poi_table t WHERE t.lat &lt; 500 </code></pre> <p>I added a table alias to make it easier to see what is an actual column vs alias.</p> <h2>Update</h2> <hr> <p>A computed column, like the one you see here:</p> <pre><code>SELECT *, ( 6371*1000 * acos( cos( radians(42.3936868308) ) * cos( radians( lat ) ) * cos( radians( lon ) - radians(-72.5277256966) ) + sin( radians(42.3936868308) ) * sin( radians( lat ) ) ) ) AS distance FROM poi_table WHERE distance &lt; 500; </code></pre> <p>...doesn't change that you can not reference a column alias in the WHERE clause. For that query to work, you'd have to use:</p> <pre><code>SELECT *, ( 6371*1000 * acos( cos( radians(42.3936868308) ) * cos( radians( lat ) ) * cos( radians( lon ) - radians(-72.5277256966) ) + sin( radians(42.3936868308) ) * sin( radians( lat ) ) ) ) AS distance FROM poi_table WHERE ( 6371*1000 * acos( cos( radians(42.3936868308) ) * cos( radians( lat ) ) * cos( radians( lon ) - radians(-72.5277256966) ) + sin( radians(42.3936868308) ) * sin( radians( lat ) ) ) ) &lt; 500; </code></pre> <p>Be aware that using a function on a column (IE: <code>RADIANS(lat)</code>) will render an index useless, if one exists on the column.</p>
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    1. COI added another (more slightly complex) example. Would your approach of aliasing the table still work? If not, what would I need to do then?
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    2. CO@rohanbk: Updated answer based on updated updated question example.
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