Prologue to Database Frameworks.


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Prologue to Database Frameworks. CS363/607* Address #2. Last class. What is a database? What is a DBMS? Database history DBMS segments Wording Information model, composition, information, DDL, DML, DBA Social database framework. Substance Relationship Model.
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Prologue to Database Systems CS363/607* Lecture #2

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Last class What is a database? What is a DBMS? Database history DBMS segments Terminology Data model, pattern, information, DDL, DML, DBA Relational database framework

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Entity-Relationship Model The E/R model permits us to outline the configuration of a database casually. Plans are pictures called element relationship outlines . Genuinely mechanical procedure to change over E/R graphs to genuine executions like social databases exist.

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Database displaying procedure

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Entity Sets Entity = “thing”, a theoretical object or some likeness thereof. Like an article in item arranged dialects. Substance set = a gathering of comparable elements. Like a class in item situated dialects. Samples: understudies, films, stars

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Attributes = properties of the substances in an element set. By and large, all elements in a set have the same properties. Traits are basic qualities, e.g. whole numbers or character strings. Illustrations: studentNo, accountNo

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Relationships are associations among two or more element sets. Case: Entity: Star, motion picture Relation: Star-in A film substance m is identified with a star element s by the relationship star-in if s shows up in motion picture m

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E/R Diagrams In an element relationship chart: Each element set is spoken to by a rectangle. Every quality of an element set is spoken to by an oval, Relationships are spoken to by jewels Edges are utilized to interface a substance to its properties furthermore join a connection boat to its element sets.

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Example Entity set Beers has two properties, name and producer. Every Beer substance has values for these two characteristics, e.g. (Budweiser, Anheuser-Busch) name maker Beers

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name addr name manf Bars Beers Sells Bars offer a few brews. permit Drinkers like a few lagers . Frequents Likes Note: permit = lager, full, none Drinkers visit a few bars . Consumers name addr Example

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Entity Set and Relationship Set The current “value” of a substance set is the arrangement of elements that have a place with it. Case: the arrangement of all bars The “value” of a relationship is an arrangement of arrangements of at present related elements, one from each of the related element sets.

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Example Bar Beer Joe’s Bar Budweiser Joe’s Bar Miller Sue’s Bar Budweiser Sue’s Bar Pete’s Ale Sue’s Bar Bud Lite

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Example name telephone ID Students stature Each understudy has four characteristics: ID, name, telephone, tallness

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Example Students Courses Sally C131 Sally C363 Joe M130 … … Taking Students Courses

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Example

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Example: An occurrence The individuals from the relationship set are the table\'s lines. For Instance, (Basic Instinct, Sharon Stone) Is a tuple in the relationship set for the present example of relationship Star-in

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Binary Relationship A paired relationship can interface any individual from one of its element sets to any individuals from the other substance set. It is the least complex relationship which just interfaces two substance sets. Illustration Student Class

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Many-Many Relationships In a numerous relationship, a substance of either set can be joined with numerous elements of the other set. Case: Think of a relationship between two element sets, for example, Sells in the middle of Bars and Beers . A bar offers numerous brews; a lager is sold by numerous bars.

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Many-One Relationships Some double connections are numerous - one starting with one substance set then onto the next. Every element of the first set is associated with at most one element of the second set. Be that as it may, a substance of the second set can be joined with zero, one, or numerous elements of the first set.

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Example Favorite , from Drinkers to Beers is numerous one. A consumer has at most one most loved lager. Be that as it may, a brew can be the most loved of any number of consumers, including zero.

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One-One Relationships In an one-one relationship, every element of either substance set is identified with at most one element of the other set. Case: Relationship Best-merchant between substance sets Manufacturers and Beers . A brew can\'t be made by more than one producer, and no maker can have more than one hit( (accept no ties).

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Example Runs Studios Presidents

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Representing “Multiplicity” Show a numerous one relationship by a bolt entering the “one” side. Demonstrate an one-one relationship by bolts entering both substance sets. In a few circumstances, we can likewise declare “exactly one,” i.e., every element of one set must be identified with precisely one element of the other set. To do as such, we utilize an adjusted bolt.

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numerous many numerous one one-one In Picture Representation of Many-One E/R: bolt indicating “one.” Rounded bolt = “exactly one.”

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Example Likes Drinkers Beers Favorite

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Example Consider Best-vender in the middle of Manufacturers and Beers . A few brews are not the smash hit of any producer so an adjusted bolt to Manufacturers would be unseemly. However, a maker needs to have a blockbuster( (we expect they are lager producers).

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In the E/R Diagram Best-vender Manufacturers Beers

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Roles Sometimes a substance set seems more than once in a relationship. Mark the edges between the relationship and the element set with names called parts .

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Relationship Set Husband Wife Bob Ann Joe Sue … … Married spouse wife Drinkers Example

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Attributes on Relationships Sometimes it is valuable to connect an ascribe to a relationship. Think about this characteristic as a property of tuples in the relationship set.

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value Sells Bars Beers value Prices Sells Bars Beers

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Multiway Relationships Sometimes, we require a relationship that interfaces more than two element sets. Assume that consumers will just drink certain lagers at specific bars. Our three twofold connections Likes, Sells, and Frequents don\'t permit us to make this qualification. Yet, a 3-way relationship would.

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name addr name manf Bars Beers permit Preferences Drinkers name addr Example

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Bar Drinker Beer Joe’s Bar Ann Miller Sue’s Bar Ann Budweiser Sue’s Bar Ann Pete’s Ale Joe’s Bar Bob Budweiser Joe’s Bar Bob Miller Joe’s Bar Cal Miller Sue’s Bar Cal Bud Lite A Typical Relationship Set

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Example Contract Stars Movies Studios (Studio, Star, Movie)

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Example

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BBP The-Bar The-Beer The-Price Bars Beers Price Converting Multiway to 2-Way Many-one connections from the uniting E.S. to the others.

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A four-way relationship

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Example

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Subclasses A substance set contains certain elements that have extraordinary properties not connected with all individuals from the set. Subclass = extraordinary case = less substances = more properties. Case: Ales are a sort of lager. Not every lager is a beer, but rather some are. Give us a chance to assume that notwithstanding every one of the properties (qualities and connections) of lagers, lagers likewise have the characteristic shading .

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Subclasses in E/R Diagrams Assume subclasses frame a tree. I.e., no various legacy. Isa triangles demonstrate the subclass relationship. Point to the superclass.

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Example Beers name producer isa Ales shading

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Example

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E/R Vs. Article Oriented Subclasses In the item arranged world, items are in one class just. Subclasses acquire properties from superclasses. Conversely, E/R substances have parts in all subclasses to which they have a place. Matters when we change over to relations.

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Pete’s Ale Example Beers name manf isa Ales shading

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Exercise 1 Let us plan a database for a bank, including data about clients and their records. Data around a client incorporates their name, address, telephone, and SSN. Records have numbers, sorts and equalizations. We likewise need to record the clients who own a record. Draw the E/R outline for this database. Make sure to incorporate bolts where suitable, to showing the variety of a relationship.

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Solution

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Summary E/R model Elements of E/R model Entity sets Attributes Relationships Entity-Relationship graph Binary and multiway connections Roles Converting multiway to twofold subclass

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Design guideline Faithfulness Avoiding excess Simplicity checks Choosing the right connections Picking up the right sort of components

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Faithfulness The configuration must be steadfast to the particulars, which is, substance sets and their traits ought to mirror the truth Examples: Stars in the middle of stars and motion pictures Teaches in the middle of courses and educators Stars-in Stars Movies Teaching Courses educators

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Avoiding repetition Not illicit, yet unsafe in light of the fact that: Take more space to store Increase unpredictability, may bring about irregularity Example: studioname claims Studios Movies name address

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Simplicity Less components is great Example: Represents possesses Movies Holdings Studios claims Movies Studios

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Choosing the right connections Entity sets can be associated with different connections, including more in the outline is bad on the grounds that: Redundancy More space utilization Modifying turns out to be more perplexing

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Example Stars-in Movies Stars Contracts possesses Studios

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Another case Stars-in Movies Stars Works-for claims Studios

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Picking the right sort of components by and large, an ascribe is less difficult to execute that an element set or a relationship, on the other hand, yo

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