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POReverse query for Hierarchical Data
 

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  1. POReverse query for Hierarchical Data
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    <p>I have seen one article <a href="http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/" rel="nofollow">http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/</a> That use below data from category table </p> <pre><code> category_id | name | parent | +-------------+----------------------+--------+ | 1 | ELECTRONICS | NULL | | 2 | TELEVISIONS | 1 | | 3 | TUBE | 2 | | 4 | LCD | 2 | | 5 | PLASMA | 2 | | 6 | PORTABLE ELECTRONICS | 1 | | 7 | MP3 PLAYERS | 6 | | 8 | FLASH | 7 | | 9 | CD PLAYERS | 6 | | 10 | 2 WAY RADIOS | 6 | </code></pre> <p>In the below query and returns below data.</p> <pre><code> SELECT t1.name AS lev1, t2.name as lev2, t3.name as lev3, t4.name as lev4 FROM category AS t1 LEFT JOIN category AS t2 ON t2.parent = t1.category_id LEFT JOIN category AS t3 ON t3.parent = t2.category_id LEFT JOIN category AS t4 ON t4.parent = t3.category_id WHERE t1.name = 'ELECTRONICS'; +-------------+----------------------+--------------+-------+ | lev1 | lev2 | lev3 | lev4 | +-------------+----------------------+--------------+-------+ | ELECTRONICS | TELEVISIONS | TUBE | NULL | | ELECTRONICS | TELEVISIONS | LCD | NULL | | ELECTRONICS | TELEVISIONS | PLASMA | NULL | | ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS | FLASH | | ELECTRONICS | PORTABLE ELECTRONICS | CD PLAYERS | NULL | | ELECTRONICS | PORTABLE ELECTRONICS | 2 WAY RADIOS | NULL | +-------------+----------------------+--------------+-------+ 6 rows in set (0.00 sec) </code></pre> <p>Now my question is if I have a table or query that has below data </p> <pre><code> +-------------+----------------------+--------------+-------+ | lev1 | lev2 | lev3 | lev4 | +-------------+----------------------+--------------+-------+ | ELECTRONICS | TELEVISIONS | TUBE | NULL | | ELECTRONICS | TELEVISIONS | LCD | NULL | | ELECTRONICS | TELEVISIONS | PLASMA | NULL | | ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS | FLASH | | ELECTRONICS | PORTABLE ELECTRONICS | CD PLAYERS | NULL | | ELECTRONICS | PORTABLE ELECTRONICS | 2 WAY RADIOS | NULL | +-------------+----------------------+--------------+-------+ </code></pre> <p>How I can make a Reverse query that returns below data: </p> <pre><code> category_id | name | parent | +-------------+----------------------+--------+ | 1 | ELECTRONICS | NULL | | 2 | TELEVISIONS | 1 | | 3 | TUBE | 2 | | 4 | LCD | 2 | | 5 | PLASMA | 2 | | 6 | PORTABLE ELECTRONICS | 1 | | 7 | MP3 PLAYERS | 6 | | 8 | FLASH | 7 | | 9 | CD PLAYERS | 6 | | 10 | 2 WAY RADIOS | 6 | </code></pre> <p>If I could have also value of level field (0 or 1 or...) in this reverse query was very good.</p> <pre><code> category_id | name | parent |position +-------------+----------------------+--------+------- | 1 | ELECTRONICS | NULL |0 | 2 | TELEVISIONS | 1 |0 | 3 | TUBE | 2 |3 | 4 | LCD | 2 |1 | 5 | PLASMA | 2 |2 </code></pre>
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