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POAutomatic sequencing of records in MySQL
 

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  1. POAutomatic sequencing of records in MySQL
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    <p>I have a MySQL table containing telephone numbers belonging to companies and individuals (customers). Each customer can have more than one telephone number, and they often want them listed in a particular order, so the table has a <code>sequence</code> field to sort each customer's telephone numbers according to their preference. The fields are:</p> <ul> <li><code>parent_id</code> - char</li> <li><code>sequence</code> - tinyint</li> <li><code>area_code</code> - string</li> <li><code>number</code> - string</li> </ul> <p>The primary key is the combination of <code>parent_id</code> and <code>sequence</code>.</p> <p>So far so good. The "problem" comes when I want to move a number up in the order, or delete a number.</p> <p>When moving a number up, the way I do it (with PHP) is changing that record's <code>sequence</code> to 0 (a customer's first telephone number is normally 1, I use 0 just for this), then incrementing the preceding number's <code>sequence</code> by 1, and then setting the original record's <code>sequence</code> to 1 less than it was. In other words, swapping the <code>sequence</code> with the preceding telephone number, but it takes three queries.</p> <p>When deleting a telephone number, I delete that record, and then I have to re-sort that customer's remaining telephone numbers so that there is no missing <code>sequence</code>. It depends on how many telephone numbers that customer has, but it can be several queries.</p> <p>I was wondering if there is a more efficient way of doing it.</p> <p>Thanks in advance!</p>
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