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    <p>There is a simple trick to collapse consecutive entries into a single group. If you group by (row_number - entry), the entries that are consecutive will end up in the same group. Here is an example demonstrating what I mean:</p> <p><strong>Query</strong>:</p> <pre><code>SELECT phonenum, @curRow := @curRow + 1 AS row_number, phonenum - @curRow from phonenums p join (SELECT @curRow := 0) r </code></pre> <p><strong>Results</strong>:</p> <pre><code>| PHONENUM | ROW_NUMBER | PHONENUM - @CURROW | ------------------------------------------------- | 27100070000 | 1 | 27100069999 | | 27100070001 | 2 | 27100069999 | | 27100070002 | 3 | 27100069999 | | 27100070003 | 4 | 27100069999 | | 27100070004 | 5 | 27100069999 | | 27100070005 | 6 | 27100069999 | | 27100070008 | 7 | 27100070001 | | 27100070009 | 8 | 27100070001 | | 27100070012 | 9 | 27100070003 | | 27100070015 | 10 | 27100070005 | | 27100070016 | 11 | 27100070005 | | 27100070040 | 12 | 27100070028 | </code></pre> <p>Notice how the entries that are consecutive all have the same value for <code>PHONENUM - @CURROW</code>. If we group on that column, and select the min &amp; max of each group, you have the summary (with one exception: you could replace the END value with <code>NULL</code> if START = END if that's a requirement):</p> <p><strong>Query</strong>:</p> <pre><code>select min(phonenum), max(phonenum) from ( SELECT phonenum, @curRow := @curRow + 1 AS row_number from phonenums p join (SELECT @curRow := 0) r ) p group by phonenum - row_number </code></pre> <p><strong>Results</strong>:</p> <pre><code>| MIN(PHONENUM) | MAX(PHONENUM) | --------------------------------- | 27100070000 | 27100070005 | | 27100070008 | 27100070009 | | 27100070012 | 27100070012 | | 27100070015 | 27100070016 | | 27100070040 | 27100070040 | </code></pre> <p>Demo: <a href="http://www.sqlfiddle.com/#!2/59b04/5">http://www.sqlfiddle.com/#!2/59b04/5</a></p>
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    1. COthanks for the brilliant answer! How do I cater for the situation where phonenum might be non-numeric such as where it might be del_2712212 or an ip address? I just want to exclude this "dirty" data for now.
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      1. USZahir J
    2. CO@Zahir: Just come up with a filter to leave that data out, and include it in a `where` clause on the inner query. You should be able to find numerous examples on the web how to validate that data is numeric. You may also need to cast it for the query to work properly, as I assumed the input data was already a numeric type.
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