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

Transcription

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

2 Additional features : Motivation Not in relational model: Structured attributes - Compound records, Sets - Sub-tables - Not 1NF! Operations (methods) Inheritance between relations - ER generalization not supported directly Activity Rules 9.2

3 Object Orientation: OO DBMS 1. Idea: - Make object oriented language persistent (direct object-oriented DBS) - Seamless integration: No difference between persistent / non-persistent objects (Programmers view) - OO Modelling and design methodology - No "tabular data abstraction" Issues - Concurrency and transactional support? - Schema? - Language support (non-oo languages?) OODBS: Object Store, Poet, O2, GemStone, Orion 9.3

4 Object Orientation: Object Relational DBMS 2. Idea: - Enhance relational model with object concepts (object-relational DBS) - Keep basis of relational DBMS (RDBMS) - Enhance RDBMS by constructed types, inheritance, methods Issues - Partially stabilizes outdated solutions - Add-on worse than new approach? - Saves investment into your (oo-)software ORDBS: Oracle, Informix, DB2 Supported by SQL-99 standard 9.4

5 OR in SQL:1999 : Constructed data types Row data type - Sequence of attribute-domain-pairs ROW(street VARCHAR(30), city VARCHAR(40)) e.g., ROW( arnim, berlin ) Collection data type - Array of similar domain-types VARCHAR(40) ARRAY[2] e.g., ARRAY[ arnim, berlin ] enhanced SQL:

6 OR in SQL:1999 : Type definition (UDT) Structured type: - Attributes and operations in single entity - Specify fields and signature of methods - Implementation of method body separately Example: CREATE TYPE CustomerNote AS( sender char(20), receiver char(20), sdate date, contents clob (1M), method abstract() returns varchar(256) FINAL; ) enhanced SQL:1999 Declares existence of function abstract() 9.6

7 OR in SQL:1999 : Type definition (UDT) Instances of UDTs - Created by system supplied constructor function - Generated automatically when defined Access to UDT attributes - Restricted to functions - Observer and mutation function automatically generated - Retrieval via dot-notation, arrow notation 9.7

8 OR in SQL:1999 : Routines Routines: - Categories: Procedures, functions, 2 method types - Signature: routine name + category + parameter list Sender attribute name Sender() observer method name Sender( anna@inter.net ) - mutator method name Example: CREATE FUNCTION abstract() RETURNS varchar(256) BEGIN DECLARE a varchar(256); SET a = substr(contents, 200); RETURN a; END; 9.8

9 OR in SQL:1999 : Type definition (UDT) Three usage models: 1. Simple UDTs for semantic distinction 2. UDTs as column construct 3. UDTs as table constructs Use UDT as column construct CREATE TABLE Correspondence ( id INTEGER PRIMARY KEY, CustomerNote ); Core SQL:1999 enhanced SQL:

10 OR in SQL:1999 : Object columns Insert row (compound statement): BEGIN DECLARE e CustomerNote; SET e = CustomerNote(); SET e = e.sender( anna@inter.net ); INSERT INTO Correspondence VALUES(001,e); END; Retrieve row: SELECT CustomerNote.sender(), CustomerNote.receiver(), FROM Correspondence WHERE id=001; 9.10

11 OR in SQL:1999 : Object tables Use UDT as table construct (typed table) - Insert and update similar to relational tables CREATE TYPE MovieType AS ( id INTEGER, title VARCHAR(60), category CHAR(10), year DATE, director VARCHAR(30), pricepday DECIMAL(4,2), length INTEGER FINAL ); CREATE TABLE Movies OF MovieType REF IS SelfReferencingColumn; 9.11

12 OR in SQL:1999 : Object tables Table referencing object table CREATE TABLE MovieTape( id INTEGER PRIMARY KEY, format CHAR(5) NOT NULL, movie REF(MovieType) ); Insert Row INSERT INTO MovieTape SELECT 001, DVD, SelfReferencingColumn FROM Movies WHERE id = 95; 9.12

13 OR in SQL:1999 : Object access Accessing object instances - Alias necessary SELECT m.movie->title FROM MovieTape m; Accessing references SELECT movie FROM MovieTape; MOVIE F5C 9.13

14 OR in SQL:1999 : Object access Accessing referenced objects: DEREF SELECT DEREF(mt.movie) FROM MovieTape mt; DEREF(MT.MOVIE)(ID, TITLE, CATEGORY, YEAR, DIRECTOR, PRICEPDAY, LENGTH) MOVIETYPE(95, 'Psycho', 'suspense', '01-JUN-69', 'Hitchcock', 2, NULL) 9.14

15 OR in SQL:1999 : Implementations MySQL: not implemented Oracle: implemented differently CREATE TYPE MovieType_oracle AS OBJECT ( id INTEGER, title VARCHAR(60), category CHAR(10), year DATE, director VARCHAR(30), pricepday DECIMAL(4,2), length INTEGER ); CREATE TABLE Movies_oracle OF MovieType_oracle; 9.15

16 OR in SQL:1999 : Implementations - Oracle Referencing table CREATE TABLE MovieTape( id INTEGER PRIMARY KEY, format CHAR(5) NOT NULL, movie REF MovieType_oracle); Insert values INSERT INTO Movies_oracle VALUES (MovieType_oracle(95, 'Psycho','suspense', to_date('1969', 'yyyy'),'hitchcock',2.00,null)); INSERT INTO MovieTape VALUES(10,'DVD',NULL); UPDATE MovieTape SET movie = (SELECT ref(m) FROM Movies_oracle m WHERE m.id = 95) WHERE id=10; 9.16

17 OR in SQL:1999 : Implementations - Oracle Adding a method - Specify IN, OUT and INOUT parameter - Pragma "Write No Database State" (WNDS) needed if function is to be used in SELECTs ALTER TYPE MovieType_oracle REPLACE AS OBJECT ( id INTEGER, title VARCHAR(60), category CHAR(10), year DATE, director VARCHAR(30), pricepday DECIMAL(4,2), length INTEGER, MEMBER FUNCTION price(days IN number) RETURN number, PRAGMA RESTRICT_REFERENCES (price, WNDS) ); 9.17

18 OR in SQL:1999 : Implementations - Oracle Implementing a method CREATE TYPE BODY MovieType_oracle AS MEMBER FUNCTION price(days IN number) RETURN NUMBER IS BEGIN RETURN days * self. pricepday; END; END; Using a method SELECT mt.id, mt.movie.price(1) FROM MovieTape mt WHERE mt.id=10; ID MT.MOVIE.PRICE(1)

19 OR in SQL:1999 : Generalization Structured types and subtypes : - Inheritance of all attributes and functions - FINAL: UDT may not have any subtypes UNDER it Examples: CREATE TYPE PersonType AS( first_name VARCHAR(16), last_name VARCHAR(24), DateOfBirth DATE NOT FINAL); CREATE TYPE WorkingPersonType UNDER PersonType AS ( PlaceOfWork VARCHAR(60), WorkPhoneNumber DECIMAL(7) NOT FINAL); enhanced SQL:

20 Object Orientation: Final remarks Inheritance, oo-concepts SQL:1999 No inheritance in Oracle and MySQL Lack of standards prevents heavy usage Object-relational technology is mature Keeps advantages of tabular data Might improve 'impedance mismatch' 9.20

21 Active Concepts: Motivation Active database - Relational or object oriented data base - Triggers actions in reaction on (system)events - ECA-Rules specify event, condition, action Applications: - Integrity Test, Referential Integrity Test - Event Logging - User Auditing, access control, security authorization - Gather statistics - modify tables according to DML statements against views - publish events to applications - but also: trigger of external actions (notify administrator about weird actions on data) 9.21

22 Active Concepts: Motivation ECA-rule structure When <event expression > If <condition expression> Then <action> Attributes {priority,...} Conceivable events: - Database state transitions - Temporal events - Abstract or external events ADBS: Sentinel, Ode, Samos Simple triggers also in SQL:1999 event condition action 9.22

23 Trigger in SQL:1999 : Introduction Simplified integrity rules Simple conditions enhanced SQL:1999 CREATE TRIGGER <TriggerName> {before after } {insert delete update} ON <RelationName> [referencing old as <OldName>, new as <NewName>] [WHEN <Condition>] [for each row statement] <SQLStatement> - called on insert/update/delete on specified relation - references: binds variables to old/new tuples of a relation - for each row: activates action for all selected tuples - for each statement: activates action once for each condition 9.23

24 Trigger in SQL:1999 : Examples Examples: CREATE TABLE moviecounter( id integer, counter integer); CREATE TRIGGER TapeCount AFTER INSERT ON Tape FOR EACH ROW update moviecounter m set m.counter = m.counter+1 where m.id=tape.movie_id ; CREATE TRIGGER Tape_trigger AFTER DELETE ON Tape REFERENCING OLD AS OldRow FOR EACH ROW INSERT INTO MyLog VALUES ( Deleted tape:, OldRow.id); 9.24

25 Trigger in SQL:1999 : Implementations MySQL: trigger not implemented Oracle: implemented differently CREATE [OR REPLACE] TRIGGER <trigger_name> {BEFORE AFTER INSTEAD OF} {INSERT DELETE UPDATE [OF <column_list>]} ON <RelationName> [[REFERENCING <attribute renaminglist>] FOR EACH ROW [WHEN (<condition>)]] [DECLARE <declarations>] BEGIN <PL/SQL code> END; 9.25

26 Trigger in SQL:1999: Implementations in Oracle Examples: CREATE or replace TRIGGER tapecount_oracle AFTER INSERT ON tape FOR EACH ROW BEGIN update moviecounter set counter=counter+1 where id= :new.movie_id; END; CREATE or replace TRIGGER Tape_trigger AFTER DELETE ON Tape REFERENCING OLD AS OldRow FOR EACH ROW BEGIN INSERT INTO MyLog VALUES ('Deleted tape:', :oldrow.id); END; variable 9.26

27 Trigger in SQL:1999: Implementations in Oracle Example: CREATE OR REPLACE TRIGGER CUSTOMER_DEL_CHECK BEFORE DELETE ON CUSTOMER FOR EACH ROW DECLARE CUSTOMER_COUNT NUMBER; BEGIN SELECT COUNT(mem_no) INTO CUSTOMER_COUNT FROM Rental WHERE mem_no = :OLD.mem_no; IF (CUSTOMER_COUNT > 0) THEN RAISE_APPLICATION_ERROR(-20000, 'Cannot delete customer because it has ' TO_CHAR(CUSTOMER_COUNT,'99999') ' Rentals.'); END IF; END; 9.27

28 Trigger in SQL:1999: Implementations in Oracle Trigger Dependencies: - trigger invalid if depended-on object modified - depended-on objects: stored procedure or function called from the trigger body, other functions or packages - invalid triggers recompiled when next invoked - if recompilation fails (object dropped) trigger becomes VALID WITH ERRORS Recompiling Triggers - manually: ALTER TRIGGER statement ALTER TRIGGER <trigger_name> COMPILE 9.28

29 Trigger in SQL:1999 : Execution Modes Cascading rule execution - Events occur during action and trigger new rules - When is the new rule executed? Iterative execution: - complete action E1 R1 R1 E2 R3 R4 - insert new rules (according priority) in list of waiting rules Recursive execution: - interrupt action - execute all immediate rules E1 R1 R1 E2 R3 R4 9.29

30 Trigger in SQL:1999 : Cascading Rules Problem: no termination of recursive rule triggering Avoid during rule definition - complicated, - needs methodology - models: finite state machine, petri-nets - and tool-support, e.g. rule analyzer Use system-internal restrictions - syntactical rule restriction, - abort if #cycles > threshold E1 R1 R1 E2 R3 R4 E4 R5 R6 E5 R7 R8 9.30

31 Trigger in SQL:1999 : Final remarks Definition complicated, error source Difficult validation Only restricted abstractions supported Definition for single operation may lead to multiple definitions No deferred execution possible Cascading triggers, cycles possible Conflict resolution problematic 9.31