Object Relational Concepts and Systems

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1 and Systems Principles Constructed Types and non first normal form relations User Defined Types Motivation Objects and Relations Object Relational Systems Principles: Keep the goodies of RDB Enhance relational systems by constructed types, inheritance, methods Supported by SQL-99 standard Issues Technologically outdated solutions stabilized e.g. type system, baroque constructs of SQL Add-on usually worse than completely new approach Important aspect: Save investment into your software by upward compatibility of.... DBS, application software ORDBS: Postgres, Oracle, Informix, DB2 hs / FUB dbsii-03-4ordbs-2

2 Object types SQL-99: Additional Types Literal types Collections: Array, List, Set and table type Lobs ("large objects"): Binary (Blob), Character (CLOB) image blob movie(2gb) Object types A row may be an object which has attributes and can be referenced CREATE TYPE AdressType AS OBJECT ( city VARCHAR(30), zipcode VARCHAR(15), street VARCHAR (30), number VARCHAR(5), country VARCHAR(15) ); / hs / FUB dbsii-03-4ordbs-3 Object Types, Object Tables Object types CREATE TYPE MovieType AS OBJECT ( mid Int, title VARCHAR(30), director VARCHAR(25), year date ); / Object table SQL> CREATE TABLE MovieObjects OF MovieType; Objects may only live in a table hs / FUB dbsii-03-4ordbs-4

3 References REFerences CREATE TABLE MovieTape ( Id Int, movie REF MovieType, since date, back date ); Table with object reference ud: 007 movie: since: back: REF types have values, can be seen by user as opposed to OO languages hs / FUB dbsii-03-4ordbs-5 References References in Oracle System generated OIDs, system wide unique values, even in a distributed environment or OIDs derived from a primary key Relationship between system generated and primary keys have to be established by application program Structure of OIDs implementation defined, don't use them explicitly hs / FUB dbsii-03-4ordbs-6

4 Object types and Tables with structured attribute types (Non First Normal Form) 1 Create TABLE TapeStruct ( 2 id INT, 3 format CHAR(5), 4 movie MovieType, 5 since date, 6* back date) 7 ; Object as Structured attribute No difference between structured types and object types SQL> CREATE OR REPLACE TYPE Foo (bar Int); 2 / Warnung: Typ wurde mit Kompilierungsfehlern erstellt. hs / FUB dbsii-03-4ordbs-7 Using Object types Type constructors Each type defined by AS OBJECT has a type constructor <objectname> Constructor wraps the fields e.g. MovieType(65, 'To be or not to be','anti-war',0.5, 'Lubitsch', todate('1942', 'YYYY')) Used in insert statement: SQL> Insert INTO MovieObjects VALUES ( MovieType(65, 'To be or not to be', 'Lubitsch', to_date('1942', 'YYYY'))) And more hs / FUB dbsii-03-4ordbs-8

5 Using Object types Inserting into tables with structured and unstructured attributes (fields) SQL> INSERT INTO TapeStruct VALUES(10,'DVD',MOVIETYPE(65, 'To be or not to be', 'Lubitsch', ' '),NULL,NULL); Doesn't work with REF attributes: object different from ref 1 INSERT INTO MovieTape VALUES(10, 2* MOVIETYPE(65, 'To be or not to be', 'Lubitsch', ' '),NULL,NULL) 3 ; MOVIETYPE(65, 'To be or not to be', 'Lubitsch', ' '),NULL,NULL) * FEHLER in Zeile 2: ORA-00932: nicht übereinstimmende Datentypen hs / FUB dbsii-03-4ordbs-9 Using Object types Inserting REFerences in two steps INSERT INTO MovieTape VALUES(10,NULL,NULL,NULL) 1 UPDATE MovieTape SET movie = 2 (SELECT ref(p) FROM MovieObjects p 3 WHERE p.mid = 65) 4* WHERE id=10 5 ; How to access fields of referenced objects? Dereferencing: SQL-99 with explicite dereferencing: MovieTape.movie->title Oracle implicitly (like Java) <MovieTape-alias>.movie.title hs / FUB dbsii-03-4ordbs-10

6 Selection of REFerenced objects SQL> SELECT m.movie.title FROM MovieTape m; MOVIE.TITLE To be or not to be References and Select Alias essential REF(x): Selecting References (!) SQL> SELECT movie FROM MovieTape; -- movie is a REF type MOVIE F5CD054159CB4F D7841FAF DEF1481E BA83DA5399F84E12 hs / FUB dbsii-03-4ordbs-11 References and Select Accessing referenced objects: DEREF operator SQL> Select DEREF(p.movie) from MovieTape p; DEREF(P.MOVIE)(MID, TITLE, DIRECTOR, YEAR) MOVIETYPE(65, 'To be or not to be', 'Lubitsch ') Accessing values of objects: VALUE operator SQL> select value(p) from movieobjects p; VALUE(P)(MID, TITLE, DIRECTOR, YEAR) MOVIETYPE(65, 'To be or not to be','lubitsch', ' ') MOVIETYPE(67, 'Jurassic Parc', 'Spielberg', ' ') hs / FUB dbsii-03-4ordbs-12

7 Select Emulation of table select select * from MovieObjects; MID TITLE DIRECTOR YEAR To be or not to be Lubitsch Jurassic Parc Spielberg Means: object tables may be queried like ordinary tables But relational tables are different from object tables even if no oo features are used hs / FUB dbsii-03-4ordbs-13 Methods An example using methods Points, lines and line length SQL> create TYPE Point_T AS OBJECT ( 2 x NUMBER, 3 y NUMBER 4 ); 5 / SQL> CREATE TYPE Line_T AS OBJECT ( 2 end1 Point_T, 3 end2 Point_T 4 (; 5 / SQL> CREATE TABLE Lines ( 2 lineid INT, 3 line Line_T); -- value, no REF hs / FUB dbsii-03-4ordbs-14

8 Methods Insertion of lines SQL> INSERT INTO Lines 2 VALUES (10, Line_T ( 3 Point_T(0.0,0.0), 4 Point_T(1.0, 2.0) 5 ) 6 ); Abstract Data Types User defined type specifies fields and the signature of methods ("Member functions") Implementation of body separately hs / FUB dbsii-03-4ordbs-15 Methods Adding of a method linelength to Type Line SQL> ALTER TYPE Line_T REPLACE AS OBJECT( 2 end1 Point_T, 3 end2 Point_T, 4 MEMBER FUNCTION linelength (scale IN NUMBER) RETURN NUMBER, 5 PRAGMA RESTRICT_REFERENCES (linelength, WNDS) 6 ); IN, OUT and INOUT parameter in signature Pragma "Write No Database State" (WNDS) needed if function is to be used in SELECTs hs / FUB dbsii-03-4ordbs-16

9 Methods Implementing a method CREATE TYPE BODY Line_T AS MEMBER FUNCTION linelength (scale NUMBER) RETURN NUMBER IS BEGIN RETURN scale * SQRT((SELF.end1.x SELF.end2.x)*(SELF.end1.x-SELF.end2.x) + (SELF.end1.y-SELF.end2.y)* (SELF.end1.y-SELF.end2.y) ); END; END; / No parameter mode in method implementation hs / FUB dbsii-03-4ordbs-17 Methods Selection with user-defined methods SELECT lineid, l.line.linelength(1.0) FROM Lines l; LINEID L.LINE.LINELENGTH(1.0) , , SELECT l.line.end1, l.line.end2 FROM Lines l WHERE l.line.linelength(1) > 1.5; LINE.END1(X, Y) LINE.END2(X, Y) POINT_T(0, 0) POINT_T(1, 2) hs / FUB dbsii-03-4ordbs-18

10 Collection types Collection Types SET, Multiset, List constructors for primitive and constructed types e.g. Phones SET (VARCHAR(20)) Polygon LIST (Point_T) Value of constructed coolection type may be regarded as a table Name Phones. Abel (432,8764). id polygon. 11 [(432,874) (101,200) (111,343)] 13 Non First Normal Form Relations hs / FUB dbsii-03-4ordbs-19 Collection Types in Oracle 9 Varrays variable number of values of some type CREATE TYPE ExtentT as VARRAY(4) OF Int; CREATE OR REPLACE TYPE Address_T AS OBJECT ( zipcode CHAR(6), ciy VARCHAR(20), street VARCHAR(25), no CHAR(5)); CREATE TABLE PhoneBook ( name VARCHAR(30), firstname VARCHAR(20), addr Address_T, phones ExtentT); hs / FUB dbsii-03-4ordbs-20

11 Using VARRAY INSERT INTO PhoneBook VALUES( 'Abel', 'Hendrik', ADDRESS_T('12347', 'Berlin', 'Takustr.','9'), ExtentT(2347, 1139)); SELECT b.name, b.addr.street, b.phones FROM PhoneBook b WHERE 2347 IN (SELECT * FROM TABLE(b.phones)); NAME ADDR.STREET PHONES Abel Takustr. EXTENSION_T(2347, 1139) No way to address by position e.g. phones[2] Cast of a varray to a table hs / FUB dbsii-03-4ordbs-21 Nested tables Nested table Table (type) used as column type CREATE TYPE Polygon_T AS TABLE OF Point_T; CREATE TABLE Polygons ( pid CHAR(5), points Polygon_T) NESTED TABLE points STORE AS PointsTab; Stored outside table Polygons, Has to be made explicit Restriction: only one level of nesting (Oracle 9i: no restriction) hs / FUB dbsii-03-4ordbs-22

12 Nested tables: another example Rel a1: NUMBER, a2: SetB CREATE TYPE SetNum_AS TABLE OF Number; CREATE TYPE B AS OBJECT (b1: INTEGER, b2 SetNum); CREATE TYPE SetB AS TABLE OF B; CREATE TABLE Rel (a1 NUMBER, a2 SetB) NESTED TABLE a2 STORE AS TabSetB (Nested Table COLUMN_VALUE STORE AS TabSetNum); hs / FUB dbsii-03-4ordbs-23 Nested Tables: insertion INSERT INTO Polygons VALUES( 'squ01', Polygon_T(Point_T(0.0, 0.0), Point_T(0.0, 1.0), Point_T(1.0, 0.0), Point_T(1.0, 1.0) ) ); Insert values of 'inner table' as a list of constructed values (here of type Point_T ) hs / FUB dbsii-03-4ordbs-24

13 Querying nested tables SELECT points FROM Polygons WHERE pid LIKE 'squ%'; -- finds all squares Querying the inner table SELECT ss.x FROM THE(SELECT points -- keyword THE FROM Polygons WHERE pid ='squ01' ) ss -- Alias for inner WHERE ss.x = ss.y; -- table -- qualification Must identify exactly one row hs / FUB dbsii-03-4ordbs-25 Querying nested tables using inner tables SELECT t.pid FROM Polygons t WHERE EXISTS (SELECT ss.x FROM TABLE(SELECT points FROM Polygons t2 WHERE t2.pid =t.pid ) ss WHERE ss.x = ss.y) AND pid <> 'squ01'; Select one row in polygons and select a table value (points) Additional outer qualification predicate Inner qualification on table value hs / FUB dbsii-03-4ordbs-26

14 insert From relations to object-relations Suppose there is a flat table CREATE TABLE LinesFlat( id INT, x1 NUMBER,y1 NUMBER,x2 NUMBER,y2 NUMBER ); INSERT INTO Lines SELECT id, Line_T(Point_T(x1,y1), Point_T(x2,y2)) FROM LinesFlat; Insertion, values supplied by SELECT, constructed by appropriate type hs / FUB dbsii-03-4ordbs-27 Collection types: insert Insertion into complex structured table Suppose, there is a flat Polygon table CREATE TABLE PolyFlat ( name VARCHAR2(20), x NUMBER, y NUMBER ); Steps to insert all the points with name 'triangle' into the Polygon Table with nested table attribute points Query PolyFlat to get all points belonging to triangle Turn the collection of answers into relation using keyword MULTISET Turn relation into a Polygon_T value by CAST AS Polygon_T hs / FUB dbsii-03-4ordbs-28

15 Inserting from a flat into a nested table INSERT INTO Polygons VALUES('square', CAST( MULTISET(SELECT x, y FROM PolyFlat WHERE name = 'square' ) AS Polygon_T ) ); hs / FUB dbsii-03-4ordbs-29 Final remarks No inheritance in Oracle 8i, but SQL-99.. and Oracle >= 9 Object-relational technology is mature Lack of standards prevents heavy usage despite SQL-99 Might improve the 'impedance mismatch' between programming languages and relational database while keeping the advantages of tabular data Use of ORDB in O/R mapping?? The more concepts the more implementations the more solutions the more bugs? Does the base Principle of RDM still hold: Keep it simple, stupid! hs / FUB dbsii-03-4ordbs-30

SQL:1999 additional features. Object-oriented concepts Object relational concepts in SQL:1999 Active database concepts Active concepts in SQL:1999

SQL:1999 additional features. Object-oriented concepts Object relational concepts in SQL:1999 Active database concepts Active concepts in SQL:1999 SQL:1999 additional features Object-oriented concepts Object relational concepts in SQL:1999 Active database concepts Active concepts in SQL:1999 Additional features : Motivation Not in relational model: