using sql to access hierarchical data structures using sql to access hierarchical data structures...

Using SQL to Access Using SQL to Access Hierarchical Data StructuresHierarchical Data Structures

(Raising SQL’s Hierarchical Data Structure Processing to that of

XML’s)

By

Michael M. David

(Speaker Notes Available, Right Click in Full Screen Mode)

Copyright 2003 by Michael M David 2

Characteristics of Hierarchical Characteristics of Hierarchical StructuresStructures

1) Root nodes have only one occurrence

2) Children nodes have only one parent node

3) Parent nodes can have multiple child nodes also known as Siblings

4) Siblings and their descendents produce multiple legs

5) Children nodes can have zero to many occurrences


Emp=3

Example Hierarchical StructureExample Hierarchical Structure

Company=1

Proj=2

Dpnd=2 Dpnd=4Dpnd=1 Dpnd=3

Proj=1 Emp=2

Emp=1


Hierarchical Structure SemanticsHierarchical Structure Semantics

1) Sibling legs are related only by their common parent node, they are independent otherwise

2) Sibling leg occurrences are not related one-to-one,

more collectively associated 3) Selection based on one sibling node occurrence selects

all sibling occurrences from the other sibling leg

4) Selection criteria based on multiple sibling legs compares all combinations of occurrences related under the lowest common parent

5) Single unambiguous path to each node


Emp=3 Emp=2

Hierarchical Query Semantics Hierarchical Query Semantics Examples 1 of 2

1) SELECT Emp, Proj WHERE Proj=22) SELECT Company WHERE Dpnd=1 AND Proj=23) SELECT Company WHERE Dpnd=1 AND Emp=2

Company=1

Proj=2

Dpnd=2 Dpnd=4Dpnd=1

Emp=1

Dpnd=3

Proj=1


Emp=3 Emp=2

Hierarchical Query SemanticsHierarchical Query Semantics Examples 2 of 2 4) SELECT Emp, Proj WHERE Emp=1 OR Proj=95) SELECT Emp, Proj WHERE Emp=8 OR Proj=26) SELECT Emp, Proj WHERE Emp=1 OR Proj=2

Company=1

Proj=2

Dpnd=2 Dpnd=4Dpnd=1

Emp=1

Dpnd=3

Proj=1


Relating Hierarchical and Relating Hierarchical and Relational Query ProcessingRelational Query Processing

Cartesian Product Based Result Sets Naturally Support Hierarchical Semantics:

1) Selection based on one sibling node occurrence selects all sibling occurrences from the other sibling leg

2) Selection based on multiple sibling legs compares all combinations of occurrences under their lowest common parent node


Relational Working Set ofRelational Working Set of:SELECT * FROM Company, Emp, Dpnd, ProjWhere CoKey=EmpCoKey AND CoKey=ProjCoKey AND EmpKey=DpndEmpKey

Company=1 Emp=1 Dpnd=1 Proj=1









Relational Queries Produce Same Relational Queries Produce Same Result as Hierarchical 1 of 2 Result as Hierarchical 1 of 2 1) SELECT Emp, Proj … WHERE Proj=22) SELECT Company … WHERE Dpnd=4 AND Proj=23) SELECT Company ... WHERE Dpnd=1 AND Emp=2










Relational Queries Produce Same Relational Queries Produce Same Result as Hierarchical Queries 2 of 2Result as Hierarchical Queries 2 of 2

4) SELECT Emp, Proj … WHERE Emp=1 OR Proj=95) SELECT Emp, Proj … WHERE Emp=8 OR Proj=26) SELECT Emp, Proj... WHERE Emp=1 OR Proj=2

Proj=2Dpnd=4Emp=2Company=1









SQL-92 Outer Join OverviewSQL-92 Outer Join Overview

SELECT … FROM TableRef [,TableRef]…

WHERE …

TableRef is: TableName | ViewName | Join1 | Join2

Join1 is: [(]TableRef JoinType Join TableRef

JoinSpec[)]

Join2 is:[(]TableRef Natural JoinType Join

TableRef [)]

JoinType is: LEFT | RIGHT | FULL | INNER

JoinSpec is: ON JoinCond | USING (ColNameList)


Describing Hierarchical StructuresDescribing Hierarchical Structures

Employee Structure:

Employee Over Company Related By CoKey=EmpCoKey Over Dependent Related By EmpKey=DpndEmpKey

Company Structure:

Company Over Employee Related By CoKey=EmpCoKey Over Dependent Related By EmpKey=DpndEmpKey

Company

Employee

Dependent

Employee

Company Dependent


Modeling Hierarchical StructuresModeling Hierarchical Structures

Employee View:

SELECT * FROM Employee LEFT JOIN Company ON CoKey=EmpCoKey LEFT JOIN Dependent ON EmpKey=DpndEmpKey

Company View:

SELECT * FROM Company LEFT JOIN Employee ON CoKey=EmpCoKey LEFT JOIN Dependent ON EmpKey=DpndEmpKey

Company

Employee

Dependent

Employee

Company Dependent


Any Data Structure Can be ModeledAny Data Structure Can be ModeledCreate View mmbook asSelect * From BookLeft Join Contents On Book=ContentsLeft Join ChapterOn Book=ChapterLeft Join Index On Book=IndexLeft Join Section On Chapter=SectionLeft Join TextOn Section=TextLeft Join Audio On Section=AudioLeft Join Scene On Section=SceneLeft Join Clip On Scene=Clip

Book

Contents Chapter Index

Section

Text Audio Scene

Clip


Data Structure ExtractionData Structure ExtractionSelect * From BookLeft Join Contents On Book=ContentsLeft Join ChapterOn Book=ChapterLeft Join Index On Book=IndexLeft Join Section On Chapter=SectionLeft Join Text On Section=TextLeft Join Audio On Section=AudioLeft Join Scene On Section=SceneLeft Join Clip On Scene=Clip

Table Table Struct Parent No. Name Level No. 1 Book 1 0 2 Content 2 1 3 Chapter 2 1 4 Index 2 1 5 Section 3 3 6 Text 4 5 7 Audio 4 5 8 Scene 4 5 9 Clip 5 8


Processing Hierarchical StructuresProcessing Hierarchical Structures

Company View:

SELECT * FROM Company LEFT JOIN Employee ON CoKey=EmpCoKey LEFT JOIN Dependent ON EmpKey=DpndEmpKey LEFT JOIN Project ON CoKey=ProjCoKey

• Left arg of Left Join preserved with missing right arg• Result of preceding joins fed into following join• Once missing value found, rest of current leg occurrence is null (missing)

Company

Employee

Dependent

Project


Working Set ofWorking Set of Company Hierarchical ViewCompany Hierarchical View

SELECT * FROM Company LEFT JOIN Employee ON CoKey=EmpCoKey LEFT JOIN Dependent ON EmpKey=DpndEmpKey LEFT JOIN Project ON CoKey=ProjCoKey WHERE Proj=1





Company=1 Emp=3 Dpnd=Null Proj=1

Company=1 Emp=3 Dpnd=Null Proj=1


Substructure SupportSubstructure SupportCREATE View EmpView as SELECT * FROM Employee LEFT JOIN Dependent

ON EmpKey=DpndEmpKey

SELECT * FROM Company LEFT JOIN EmpView ON CoKey=EmpCoKey SELECT * FROM Company LEFT JOIN Employee LEFT JOIN Dependent ON EmpKey=DpndEmpKey ON CoKey=EmpCoKey

Company

Employee

Dependent


Hierarchical Access OptimizationHierarchical Access Optimization

Create View CoView ASSELECT * FROM CompanyLEFT JOIN Project ON CoKey=ProjCoKeyLEFT JOIN Employee ON CoKey=EmpCoKeyLEFT JOIN Dependent ON EmpKey=DpndEmpKey

Optimized View:SELECT CoName, DpndName From CoView

SELECT CoName, CoName FROM Company LEFT JOIN Employee ON CoKey=EmpCoKeyLEFT JOIN Dependent ON EmpKey=DpndEmpKey

Company

Project Employee

Dependent

Company

Employee

Dependent


Hierarchical Data FilteringHierarchical Data FilteringSELECT * FROM CompanyLEFT JOIN Project ON CoKey=ProjectCoKey

AND ProjType=“Software”LEFT JOIN Employee ON CoKey=EmpCoKey

AND EmpStat=“Fulltime”LEFT JOIN Dependent ON EmpKey=DpndEmpKey

Company

Project Employee

Dependent


SQL to XML MappingSQL to XML MappingSELECT * FROM EmployeeLEFT JOIN CompanyON CoKey=EmpCoKeyLEFT JOIN DependentON EmpKey=DpndEmpKeyFOR XML Element Mapping

Employee DataEmp Co DpndF DpndLMike CoA Jay RoeMike CoA Jane DoeMary CoA Sam Foe

<?xml Version=‘1.0’?><EmpView><Employee><Emp>Mike</Emp><Company>CoA</Company><Dependent><Dpndf>Jay</DpndF><DpndL>Roe</DpndL></Dependent>

:


XML to SQL MappingXML to SQL MappingSELECT * FROM EmployeeLEFT JOIN CompanyON CoKey=EmpCoKeyLEFT JOIN DependentON EmpKey=DpndEmpKey



:


SQL-Based Access of XMLSQL-Based Access of XMLSELECT * FROM EmployeeLEFT JOIN CompanyON CoKey=EmpCoKeyLEFT JOIN DependentON EmpKey=DpndEmpKey



:


Element Node PromotionElement Node Promotion

SELECT X, Z FROM ViewX

ViewX modeled Structure Output Structure

X

Y

Z

X

Z


Native XML IntegrationNative XML IntegrationSELECT * FROM ViewR LEFT JOIN ViewXN ON …

A

B C X

Y Z

A B C X Y Z

A

B C

X

Y Z

A B C XYZGet XML

Client … ViewR LEFT JOIN ViewX … Server

Relational XML

Native XML

Output XML Doc


Joinless Native XML AccessJoinless Native XML Access

B1

A1

B2C1

C2

A1 B1 C1 A1 B1 C2 A1 B2 C1 A1 B2 C2

A2

B3B4

C3C4

A2 B3 C3 A2 B3 C4 A2 B4 C3 A2 B4 C4

SQL Engine


Modeling Duplicate Element nodes Modeling Duplicate Element nodes Using Hierarchical StructuresUsing Hierarchical Structures

SELECT Addr1, Addr2 From Company

LEFT JOIN Department ON CoKey=DeptCoKey

LEFT JOIN Employee ON CoKey=EmpCoKey

LEFT JOIN Address AS Addr1

ON Addr1.AddrKey=DeptAddrKey

LEFT JOIN Address AS Addr2

ON Addr2.AddrKey=EmpAddrKey

Company

Department Employee

Addr2Addr1


Modeling IDREFed Element Nodes Modeling IDREFed Element Nodes Using Hierarchical StructuresUsing Hierarchical Structures

SELECT * From Department LEFT JOIN Project AS Proj1 ON DeptKey=ProjDeptKey LEFT JOIN Employee ON DeptKey=EmpDeptKey LEFT JOIN Project AS Proj2 ON EmpKey=Proj2.IDRefEmp <Department> ….<Proj ID=“X”> … <Proj/><Proj ID=“Y”> … <Proj/><Employee IDREFS=“X,Y”> John <Employee/>

Department

Proj1 Employee

Proj2


Symmetric Table LinkingSymmetric Table Linking

SELECT * FROM CompanyLEFT JOIN EmployeeX FULL JOIN EmployeeY Using (EmpKey)ON CoKey=EmpCoKeyLEFT JOIN DependentOn EmpKey=DpndEmpKey

• Allows flat structures to be specified in the structure

• Flat substructures are created by the Full and Inner joins

Company

EmployeeX EmployeeY

Dependent


Variable Structures

SELECT * FROM Publisher

LEFT JOIN Book ON PubKey=BookFKey

AND PublishType=“Book”

LEFT JOIN SONG PubKey=SongFKey

AND PublishType=“SONG”

Publisher Publisher

Book Song

This dynamic structure controlled by flag in root


SQL-Powered Hierarchical SQL-Powered Hierarchical Processing EngineProcessing Engine

If SQL can perform hierarchical processing-

it can also drive a hierarchical engine for:• More accurate hierarchical results• Increased execution and memory efficiency• Heterogeneous and disparate access• Truly seamless integrated access• Distributed processing with linear scaling• Extended Support for XML irregular structure


SQL Hierarchical ProcessingSQL Hierarchical ProcessingSELECT * FROM CompanyLEFT JOIN EmployeeON CoKey=EmpCoKeyLEFT JOIN DependentON EmpKey=DpndEmpKey

Co Emp DpndF DpndLXYZ Mike Jay Roe Jane Doe Mary Sam FoeABC John ---- ----LMN ---- ---- ----

Mike XYZ Mary XYZ John ABC

Jay Roe Mike Jane Doe Mike Sam Foe Mary

XYZ ABC LMN


Suggested Hierarchical Ordering Support

SELECT * FROM A

ORDER BY A.fld

LEFT JOIN B ON A=B

ORDER BY B.fld

LEFT JOIN C ON B=C

ORDER BY C.fld

• Each node can be separately ordered• Ordering B does not unorder C

A

B C


Suggested Hierarchical Quantifier Support

SELECT * FROM Dept

LEFT JOIN Emp

ON DeptNo=EmpDeptNo

LEFT JOIN Dpnd

ON EmpNo=DpndDeptNo

Where Dept HAS ALL DpndStatus=“Active”

Dept

EMP

Dpnd


RecapRecap

The following features allow the ANSI SQL-92 outer join complete control over processing data structures and XML:

Structure Modeling Structure Processing Joining Structures Variable Structures Symmetric Linking

Hierarchical Filtering Substructure Modeling Access Optimization Element Sharing Heterogeneous Access


For more information refer to the book:

Advanced ANSI SQL Data Modeling and Structure

Processing

From Artech-House Publishers

using sql to access hierarchical data structures using sql to access hierarchical data structures...

Documents

sibling occurrences

hierarchical semantics

hierarchical queries

multiple sibling legs

dpndempkey company structure

hierarchical data structures

sibling leg occurrences

sibling node occurrence