DATEDIFF - Replace NULL with NOW()

<p>I got following SQL Query</p><pre><br /><code>SELECT<br /> e.id,<br /> c.name,<br /> e.location,<br /> e.designation,<br /> e.time_period_from,<br /> e.time_period_to,<br /> DATEDIFF(e.time_period_to, time_period_from) AS tenure_in_days<br />FROM<br /> employment e<br />LEFT JOIN<br /> company c ON (c.id = e.company_id)<br />LIMIT<br /> 0, 10<br /></code><br /></pre><p>This is working perfectly, i have a scenario where <code>time_period_to</code> can have <code>NULL</code> values, in this case, i want to replace it with current date.</p><p>Here is what i tried.</p><pre><br /><code>SELECT<br /> e.id,<br /> c.name,<br /> e.location,<br /> e.designation,<br /> e.time_period_from,<br /> e.time_period_to,<br /> DATEDIFF(IF(ISNULL(e.time_period_to), NOW(), e.time_period_from)) AS tenure_in_days<br />FROM<br /> employment e<br />LEFT JOIN<br /> company c ON (c.id = e.company_id)<br />LIMIT<br /> 0, 10<br /></code><br /></pre><p>This gives me the following error</p><pre><br /><code>ERROR 1582 (42000): Incorrect parameter count in the call to native function 'DATEDIFF'<br /></code><br /></pre><p>Where am i going wrong?</p><br /><h2>Click here view more answers <a href="%20http://stackoverflow.com/questions/34525443/datediff-replace-null-with-now">http://ift.tt/1Jfjf29</a></h2>