MySQL Cumulative Total
<p>A company rewards one of its employees every day.  The data is maintained in a table called <code>REWARDS</code>.  As shown in the sample data below, we have one row per day in the table with the following structure:</p>

<p>(Sorry for the poor table formatting)</p>

<pre><code>REWARD_DATE EMP_ID  REWARD_AMT
1-Jan-15    101       400
2-Jan-15    102       300
3-Jan-15    101       700
4-Jan-15    102       500
5-Jan-15    103       100
</code></pre>

<p>Can you write a query to report the running totals as the following?</p>

<pre><code>REWARD_DATE #EMP    TOT_REWARD_AMT
1-Jan-15    1            400
2-Jan-15    2            700
3-Jan-15    2           1400
4-Jan-15    2           1900
5-Jan-15    3           2000
</code></pre>