Active Database Concepts and Triggers

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● Chapter 24
● Outline
● Active Database Concepts and Triggers
● Event-Condition-Action (ECA) Model
● Trigger Example
● Example: Trigger Definition
● CREATE or ALTER TRIGGER
● Conditions
● Row-Level versus Statement-level
● Condition
● Action
● Triggers on Views
● Active Database Concepts and Triggers
● Temporal Database Concepts
● Spatial and Multimedia Databases
● Spatial Databases
● Multimedia Databases
● Introduction to Deductive Databases
● Overview of Deductive Databases
● Prolog/Datalog Notation
● Figure 24.11
● Datalog Notation
● Clausal Form and Horn Clauses
● Interpretation of Rules
● Proving a new fact
● Interpretation of Rules
● Minimal model
● Datalog Programs and Their Safety
● Use the Relational Operations
● Evaluation of Non-recursive Datalog Queries
● Recap

نوع زبان: انگلیسی حجم: 1.96 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 60 صفحه
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گروه موضوعی: زمان استخراج مطلب: 2019/06/05 11:05:30

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trigger, database, copyright, ramez, shamkant, elmasrus, b., navathe, time, condition, ., concept,

توجه: این مطلب در تاریخ 2019/06/05 11:05:30 به صورت خودکار از فضای وب آشکار توسط موتور جستجوی پاورپوینت جمع آوری شده است و در صورت اعلام عدم رضایت تهیه کننده ی آن، طبق قوانین سایت از روی وب گاه حذف خواهد شد. این مطلب از وب سایت زیر استخراج شده است و مسئولیت انتشار آن با منبع اصلی است.

https://www.cs.purdue.edu/homes/ake/cs348/Chapter24.ppt

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copyright ۲ ۷ ramez elmasri and shamkant b. navathe chapter ۲۴ enhanced data models for advanced applications copyright ۲ ۷ ramez elmasri and shamkant b. navathe outline active database triggers temporal databases spatial and multimedia databases deductive databases copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers generalized model for active databases and oracle triggers triggers are executed when a specified condition occurs during insert delete update triggers are action that fire automatically based on these conditions copyright ۲ ۷ ramez elmasri and shamkant b. navathe event condition action eca model generalized model contd. triggers follow an event condition action eca model event database modification e.g. insert delete update condition any true false expression optional if no condition is specified then condition is always true action sequence of sql statements that will be automatically executed copyright ۲ ۷ ramez elmasri and shamkant b. navathe trigger example generalized model contd. when a new employees is added to a department modify the total sal of the department to include the new employees salary logically this means that we will create a trigger let us call the trigger total sal۱ this trigger will execute after insert on employee table it will do the following for each row when new.dno is not null the trigger will update department by setting the new total sal to be the sum of old total sal and new. salary where the dno matches the new.dno condition copyright ۲ ۷ ramez elmasri and shamkant b. navathe example trigger definition create trigger total sal۱ after insert on employee for each row when new.dno is not null update department set total sal total sal new. salary where dno new.dno the condition the action can be for after instead of can be insert update delete can be create or alter copyright ۲ ۷ ramez elmasri and shamkant b. navathe create or alter trigger generalized model contd. create trigger name creates a trigger alter trigger name alters a trigger assuming one exists create or alter trigger name creates a trigger if one does not exist alters a trigger if one does exist works in both cases whether a trigger exists or not copyright ۲ ۷ ramez elmasri and shamkant b. navathe conditions generalized model contd. after executes after the event before executes before the event instead of executes instead of the event note that event does not execute in this case e.g. used for modifying views copyright ۲ ۷ ramez elmasri and shamkant b. navathe row level versus statement level generalized model contd. triggers can be row level for each row specifies a row level trigger statement level default when for each row is not specified row level triggers executed separately for each affected row statement level triggers execute once for the sql statement copyright ۲ ۷ ramez elmasri and shamkant b. navathe condition generalized model contd. any true false condition to control whether a trigger is activated on not absence of condition means that the trigger will always execute for the even otherwise condition is evaluated before the event for before trigger after the event for after trigger copyright ۲ ۷ ramez elmasri and shamkant b. navathe action generalized model contd. action can be one sql statement a sequence of sql statements enclosed between a begin and an end action specifies the relevant modifications copyright ۲ ۷ ramez elmasri and shamkant b. navathe triggers on views generalized model contd. instead of triggers are used to process view modifications copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers design and implementation issues for active databases an active database allows users to make the following changes to triggers rules activate deactivate drop copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers design and implementation issues for active databases an event can be considered in ۳ ways immediate consideration deferred consideration detached consideration copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers design and implementation issues contd. immediate consideration part of the same transaction and can be one of the following depending on the situation before after instead of deferred consideration condition is evaluated at the end of the transaction detached consideration condition is evaluated in a separate transaction copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers potential applications for active databases notification automatic notification when certain condition occurs enforcing integrity constraints triggers are smarter and more powerful than constraints maintenance of derived data automatically update derived data and avoid anomalies due to redundancy e.g. trigger to update the total sal in the earlier example copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers triggers in sql ۹۹ can alias variables inside the referencinfg clause copyright ۲ ۷ ramez elmasri and shamkant b. navathe active database concepts and triggers trigger examples copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts time representation calendars and time dimensions time is considered ordered sequence of points in some granularity use the term choronon instead of point to describe minimum granularity copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts time representation … contd. a calendar organizes time into different time units for convenience. accommodates various calendars gregorian western chinese islamic hindu jewish etc. copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts time representation … contd. point events single time point event e.g. bank deposit series of point events can form a time series data duration events associated with specific time period time period is represented by start time and end time copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts time representation … contd. transaction time the time when the information from a certain transaction becomes valid bitemporal database databases dealing with two time dimensions copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts incorporating time in relational databases using tuple versioning add to every tuple valid start time valid end time copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts copyright ۲ ۷ ramez elmasri and shamkant b. navathe temporal database concepts incorporating time in object oriented databases using attribute versioning a single complex object stores all temporal changes of the object time varying attribute an attribute that changes over time e.g. age non time varying attribute an attribute that does not changes over time e.g. date of birth copyright ۲ ۷ ramez elmasri and shamkant …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: trigger, database, copyright, ramez, shamkant, elmasrus, b., navathe, time, condition, ., concept,

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https://www.cs.purdue.edu/homes/ake/cs348/Chapter24.ppt

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