 <p>You should not be storing numeric data as a string but if you do, then you will need to <code>cast()</code> it to apply a <code>SUM()</code> aggregate to it:</p> <pre><code>SELECT SUM(CAST(yourcolumn AS DECIMAL(10, 2))) FROM yourtable </code></pre> <p>So your query will be:</p> <pre><code>select sum(cast(qty as DECIMAL(10, 2))) from inventory i where i.refDocNum = 485 and i.refApp = 'WO' and i.type in (20, 21) </code></pre>