2. .Object * id . name , . , Relation * parent . child 3. . , .
. 4. ? . . . ... 5. Photo by
http://www.flickr.com/photos/shannonpatrick17/ 6. CONNECT BY Oracle
employee SELECT nameemployee_idFROM employeenameSTART WITH name =
'John' manager CONNECT BY PRIOR employee_id = manager John, , ,
etc. LEVEL . 7. CONNECT BY , . , . Oracle. 8. Common Table
Expressions WITH t( employee, name ) AS ( SELECTemployee_id, name
FROMemployee WHERE name = 'John' UNION ALL SELECTnext.employee_id,
next.name FROMemployee as nextINNER JOIN t ON t.employee_id =
next.manager ) SELECT name FROM t SELECT CTE START WITH, CONNECT BY
PRIOR. 9. CTE CONNECT BY . . UNION ALL , . CTE , (MySQL, Firebird,
PostgreSQL .). 10. , . CTE. . , . 11. ... . , , . 12. ? . : Lineage
(materialized path) 13. Lineage () -
http://www.sqlteam.com/article/more-trees-hierarchies-in-sql
EmployeeIDNameBossID Denis Eaton-Hogg1001Denis Eaton-HoggNULL Bobbi
Flekman Ian Faith1002Bobbi Flekman 1001David St. Hubbins1003Ian
Faith 1002Nigel TufnelDerek Smalls1004David St. Hubbins
10031005Nigel Tufnel10031006Derek Smalls1003 Node
ParentNodeEmployeeID DepthLineage100NULL1001 0/101100 1002
1/100/102101 1003 2/100/101/103102 1004 3/100/101/102/104102 1005
3/100/101/102/105102 1006 3/100/101/102/ 14. Lineage . . . . . 15.
ID Name ParentID 1 1NULL2 2 13 5 3 16 4 1 4 537 8 6 3 -
http://www.osp.ru/os/2003/04/182942/7 48 41 1 16 ID LeftRightLevel
IsLeaf11 16 1 N22 32 Y 2 2 3 4 3 9104 1534 92 N41015 2 N55 63 Y67
83 Y 5 5 6 7 6 8 11 712 13 8 1471112 3 Y81314 3 Y 16. . . . 17.
Image by http://www.flickr.com/photos/36041246@N00/3344 18. Object
RelationMapidparentnamechilddistancecount Relationparentchild 19. .
. covering index. . Object RelationMapidparent namechild distance.
count 20. 1 , . 2 3 4 5 . 6 7 . . 21. 7 8A 1 : 8 7 ( 1). 3 8 7 , 45
7. 7, 7.8 22. 7 8 8 7 ( 1). B 1 8 7 ( + 1). 3 7 8 4 5 ( + 1). , 7,
7 9 A, . 8 9 3 8 9 A 7 1. 23. Bx 1 7 x cx 3 dx, 45 y 8 cy dy, 7 y x
cx*cy dx+dy+1. 8: 1 * 2 = 2 9 A : 1 + 2 +1 = 4y 24. parent - child
: foreachx in descendants( child ), dx in distances( x, child ),y
in ancestors( parent ), dy in distances( parent, y )
count(x,child,dx)*count(parent,y,dy) x y dx+dy+1. count(x,y,d) x y
d ancestors(x) descendants(x) x distances(x, x) == [ ] 25. Object
RelationMapidparentnamechilddistancecount Relationparent
RelationMap child . . 26. SQL: SELECT d.child, a.parent, a.distance
+ d.distance + 1,sum( a.count * d.count ) FROM ( SELECT * FROM
RelationMap WHEREchild = @iParent UNION SELECT @iParent, @iParent,
0, 1) AS a,( SELECT * FROM RelationMap WHEREparent = @iChild UNION
SELECT @iChild, @iChild, 0, 1) AS d GROUP BY d.object, a.ancestor,
a.distance + d.distance + 1 27. , @iParent . 0 1. , @iChild . . , .
, . , . . 28. SQL: UPDATE RelationMap SETcount = om.count +
st.count FROM @tSubTree st JOIN RelationMap om ON st.child =
om.child ANDst.parent = om.parent ANDst.distance =
om.distanceINSERT INTO RelationMap SELECT st.child, st.parent,
st.distance, st.count FROM @tSubTree st LEFT JOIN RelationMap om ON
st.child = om.child ANDst.parent = om.parent ANDst.distance =
om.distance WHERE om.child IS NULL 29. SQL: UPDATE RelationMap
SETcount = om.count - st.count FROM @tSubTree st JOIN RelationMap
om ON st.child = om.child ANDst.parent = om.parent ANDst.distance =
om.distanceDELETE FROM RelationMap WHEREcount = 0 30. . . . . , ,
@iParent @iChild (.. ). . 31. , . RelationMap, . , . 32. . . . :
http://blogs.byte-force.com/files/folders/articles_ru/entry1148.aspx
