How do i calculate a projection sum using sql?
<p>I have the following Lease table</p>

<pre><code>Lease_id Apt_id Resident_id Start_Date End_Date   Upfront_Amt Monthly_Fee
101      110    1001        02/01/2015 07/31/2015 250          500
102      111    1002        03/01/2015 02/29/2016 1000         2000
103      112    1003        04/01/2015 03/31/2016 750          1500
</code></pre>

<p>What I wanted to calculate was a projection of earnings from the Monthly fee.
For example:</p>

<pre><code>01/2015 0 (No lease active)
02/2015 500 (From Lease 101)
03/2015 500 + 2000 (From Lease 101 and 102)
04/2015 500 + 2000 + 1500 (From Lease 101, 102 and 103)
:
:
08/2015 2000 + 1500 (From lease 102 and 103)
etc..
</code></pre>

<p>Is there a way to do this efficiently with a single query?</p>