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2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 1 Managing Hierarchical Data in MySQL Mike Hillyer - MySQL AB.

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Presentation on theme: "2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 1 Managing Hierarchical Data in MySQL Mike Hillyer - MySQL AB."— Presentation transcript:

1 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 1 Managing Hierarchical Data in MySQL Mike Hillyer - MySQL AB

2 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 2 About Me Member of the MySQL AB Documentation Team MySQL Core and Pro Certified MySQL Expert at www.experts-exchange.com Resident MySQL Expert at SearchDatabase.com http://www.openwin.org/mike/aboutme.php Mike Hillyer, BSc

3 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 3 About You Currently use MySQL? Another RDBMS? Manage hierarchical data? Will be managing hierarchical data? Know what hierarchical data is? How many of you…

4 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 4 About This Session http://www.openwin.org/mike/index.php/presentations/ http://dev.mysql.com/tech-resources/articles/hierarchical-data.html What is hierarchical data? The Adjacency List Model The Nested Set Model Querying the Nested Set Model –Adding New Nodes –Deleting Nodes –Additional Resources

5 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 5 What is Hierarchical Data? Data that maintains a parent-child relationship Nodes have zero or one parent, zero to many children Only the root node has no parent Various types of data –Mailing list/forum threads –Organizational charts –Content management categories –Product categories

6 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 6 Product Categories

7 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 7 The Adjacency List Model +-------------+----------------------+--------+ | 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 | +-------------+----------------------+--------+

8 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 8 Full Tree 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)

9 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 9 Leaf Nodes SELECT t1.name FROM category AS t1 LEFT JOIN category as t2 ON t1.category_id = t2.parent WHERE t2.category_id IS NULL; +--------------+ | name | +--------------+ | TUBE | | LCD | | PLASMA | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | +--------------+

10 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 10 Single Path 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' AND t4.name = 'FLASH'; +-------------+----------------------+-------------+-------+ | lev1 | lev2 | lev3 | lev4 | +-------------+----------------------+-------------+-------+ | ELECTRONICS | PORTABLE ELECTRONICS | MP3 PLAYERS | FLASH | +-------------+----------------------+-------------+-------+ 1 row in set (0.01 sec)

11 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 11 Limitations of Adjacency Lists Adjacency list model not normalized. Deleting nodes can orphan children. Querying paths and trees requires multiple self-joins. Procedural code required for most use-cases.

12 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 12 Nested Sets

13 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 13 Nested Set Table +-------------+----------------------+-----+-----+ | category_id | name | lft | rgt | +-------------+----------------------+-----+-----+ | 1 | ELECTRONICS | 1 | 20 | | 2 | TELEVISIONS | 2 | 9 | | 3 | TUBE | 3 | 4 | | 4 | LCD | 5 | 6 | | 5 | PLASMA | 7 | 8 | | 6 | PORTABLE ELECTRONICS | 10 | 19 | | 7 | MP3 PLAYERS | 11 | 14 | | 8 | FLASH | 12 | 13 | | 9 | CD PLAYERS | 15 | 16 | | 10 | 2 WAY RADIOS | 17 | 18 | +-------------+----------------------+-----+-----+

14 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 14 Numbered Sets

15 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 15 Numbered Tree

16 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 16 Full Tree SELECT node.name FROM nested_category AS node, nested_category AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt AND parent.name = 'ELECTRONICS' ORDER BY node.lft; +----------------------+ | name | +----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | PORTABLE ELECTRONICS | | MP3 PLAYERS | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | +----------------------+

17 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 17 Leaf Nodes SELECT name FROM nested_category WHERE rgt = lft + 1; +--------------+ | name | +--------------+ | TUBE | | LCD | | PLASMA | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | +--------------+

18 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 18 Node Depth SELECT node.name, (COUNT(parent.name) - 1) AS depth FROM nested_category AS node, nested_category AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt GROUP BY node.name ORDER BY node.lft; +----------------------+-------+ | name | depth | +----------------------+-------+ | ELECTRONICS | 0 | | TELEVISIONS | 1 | | TUBE | 2 | | LCD | 2 | | PLASMA | 2 | | PORTABLE ELECTRONICS | 1 | | MP3 PLAYERS | 2 | | FLASH | 3 | | CD PLAYERS | 2 | | 2 WAY RADIOS | 2 | +----------------------+-------+

19 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 19 Indented Nodes SELECT CONCAT( REPEAT(' ', COUNT(parent.name) - 1), node.name) AS name FROM nested_category AS node, nested_category AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt GROUP BY node.name ORDER BY node.lft; +-----------------------+ | name | +-----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | PORTABLE ELECTRONICS | | MP3 PLAYERS | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | +-----------------------+

20 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 20 Depth of a Sub-Tree SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth FROM nested_category AS node, nested_category AS parent, nested_category AS sub_parent, ( SELECT node.name, (COUNT(parent.name) - 1) AS depth FROM nested_category AS node, nested_category AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt AND node.name = 'PORTABLE ELECTRONICS' GROUP BY node.name ORDER BY node.lft )AS sub_tree WHERE node.lft BETWEEN parent.lft AND parent.rgt AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt AND sub_parent.name = sub_tree.name GROUP BY node.name ORDER BY node.lft;

21 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 21 Depth of a Sub-Tree - II +----------------------+-------+ | name | depth | +----------------------+-------+ | PORTABLE ELECTRONICS | 0 | | MP3 PLAYERS | 1 | | FLASH | 2 | | CD PLAYERS | 1 | | 2 WAY RADIOS | 1 | +----------------------+-------+

22 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 22 Immediate Subordinates GROUP BY node.name HAVING depth <= 1 ORDER BY node.lft; +----------------------+-------+ | name | depth | +----------------------+-------+ | PORTABLE ELECTRONICS | 0 | | MP3 PLAYERS | 1 | | CD PLAYERS | 1 | | 2 WAY RADIOS | 1 | +----------------------+-------+

23 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 23 Aggregate Functions SELECT * FROM product; +------------+-------------------+-------------+ | product_id | name | category_id | +------------+-------------------+-------------+ | 1 | 20" TV | 3 | | 2 | 36" TV | 3 | | 3 | Super-LCD 42" | 4 | | 4 | Ultra-Plasma 62" | 5 | | 5 | Value Plasma 38" | 5 | | 6 | Power-MP3 128mb | 7 | | 7 | Super-Shuffle 1gb | 8 | | 8 | Porta CD | 9 | | 9 | CD To go! | 9 | | 10 | Family Talk 360 | 10 | +------------+-------------------+-------------+

24 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 24 Aggregate Functions - II SELECT parent.name, COUNT(product.name) FROM nested_category AS node, nested_category AS parent, product WHERE node.lft BETWEEN parent.lft AND parent.rgt AND node.category_id = product.category_id GROUP BY parent.name ORDER BY node.lft; +----------------------+---------------------+ | name | COUNT(product.name) | +----------------------+---------------------+ | ELECTRONICS | 10 | | TELEVISIONS | 5 | | TUBE | 2 | | LCD | 1 | | PLASMA | 2 | | PORTABLE ELECTRONICS | 5 | | MP3 PLAYERS | 2 | | FLASH | 1 | | CD PLAYERS | 2 | | 2 WAY RADIOS | 1 | +----------------------+---------------------+

25 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 25 Adding Nodes

26 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 26 Adding a Sibling LOCK TABLE nested_category WRITE; SELECT @myRight := rgt FROM nested_category WHERE name = 'TELEVISIONS'; UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myRight; UPDATE nested_category SET lft = lft + 2 WHERE lft > @myRight; INSERT INTO nested_category(name, lft, rgt) VALUES('GAME CONSOLES', @myRight + 1, @myRight + 2); UNLOCK TABLES; +-----------------------+ | name | +-----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | GAME CONSOLES | | PORTABLE ELECTRONICS | | MP3 PLAYERS | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | +-----------------------+

27 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 27 Adding a Child LOCK TABLE nested_category WRITE; SELECT @myLeft := lft FROM nested_category WHERE name = '2 WAY RADIOS'; UPDATE nested_category SET rgt = rgt + 2 WHERE rgt > @myLeft; UPDATE nested_category SET lft = lft + 2 WHERE lft > @myLeft; INSERT INTO nested_category(name, lft, rgt) VALUES('FRS', @myLeft + 1, @myLeft + 2); UNLOCK TABLES; +-----------------------+ | name | +-----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | GAME CONSOLES | | PORTABLE ELECTRONICS | | MP3 PLAYERS | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | | FRS | +-----------------------+

28 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 28 Deleting a Leaf Node LOCK TABLE nested_category WRITE; SELECT @myLeft := lft, @myRight := rgt, @myWidth := rgt - lft + 1 FROM nested_category WHERE name = 'GAME CONSOLES'; DELETE FROM nested_category WHERE lft BETWEEN @myLeft AND @myRight; UPDATE nested_category SET rgt = rgt - @myWidth WHERE rgt > @myRight; UPDATE nested_category SET lft = lft - @myWidth WHERE lft > @myRight; UNLOCK TABLES; +-----------------------+ | name | +-----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | PORTABLE ELECTRONICS | | MP3 PLAYERS | | FLASH | | CD PLAYERS | | 2 WAY RADIOS | | FRS | +-----------------------+

29 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 29 Deleting a Parent and all Children LOCK TABLE nested_category WRITE; SELECT @myLeft := lft, @myRight := rgt, @myWidth := rgt - lft + 1 FROM nested_category WHERE name = 'MP3 PLAYERS'; DELETE FROM nested_category WHERE lft BETWEEN @myLeft AND @myRight; UPDATE nested_category SET rgt = rgt - @myWidth WHERE rgt > @myRight; UPDATE nested_category SET lft = lft - @myWidth WHERE lft > @myRight; UNLOCK TABLES; +-----------------------+ | name | +-----------------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | PORTABLE ELECTRONICS | | CD PLAYERS | | 2 WAY RADIOS | | FRS | +-----------------------+

30 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 30 Deleting a Parent and Promoting all Children LOCK TABLE nested_category WRITE; SELECT @myLeft := lft, @myRight := rgt, @myWidth := rgt - lft + 1 FROM nested_category WHERE name = 'PORTABLE ELECTRONICS'; DELETE FROM nested_category WHERE lft = @myLeft; UPDATE nested_category SET rgt = rgt - 1, lft = lft - 1 WHERE lft BETWEEN @myLeft AND @myRight; UPDATE nested_category SET rgt = rgt - 2 WHERE rgt > @myRight; UPDATE nested_category SET lft = lft - 2 WHERE lft > @myRight; UNLOCK TABLES; +---------------+ | name | +---------------+ | ELECTRONICS | | TELEVISIONS | | TUBE | | LCD | | PLASMA | | CD PLAYERS | | 2 WAY RADIOS | | FRS | +---------------+

31 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 31 Advanced Use Cases Move an entire sub-tree Handle high insert/delete volumes –Calculate gaps –Use floats –See the resources next slide

32 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 32 Credit & Resources Joe Celko's Trees and Hierarchies in SQL for Smarties http://www.openwin.org/mike/index.php/books/ http://www.sitepoint.com/article/hierarchical-data-database http://www.dbmsmag.com/9603d06.html http://www.dbmsmag.com/9604d06.html http://www.dbmsmag.com/9605d06.html http://www.intelligententerprise.com/001020/celko.jhtml http://searchdatabase.techtarget.com/tip/1,289483,sid13_gci537290,00.html http://searchdatabase.techtarget.com/tip/1,289483,sid13_gci801943,00.html http://www.klempert.de/php/nested_sets_demo http://dev.e-taller.net/dbtree/ http://www.dbazine.com/oracle/or-articles/tropashko4 http://dev.mysql.com/tech-resources/articles/hierarchical-data.html

33 2006­03-08 | Managing Hierarchical Data | © MySQL AB 2005 | www.mysql.com 33 Conclusion http://www.openwin.org/mike/presentations/ Questions?

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