Section 6 The Social Database Model: Extra Ideas.


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6-2. Section Objectives. Depict how unary and ternary connections are actualized in a social database. Clarify the idea of referential trustworthiness. Portray how the referential trustworthiness limit, course, and set-to-invalid erase principles work in a social database. . 6-3. General Hardware Co. counting OFFICE.
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Section 6 The Relational Database Model: Additional Concepts Fundamentals of Database Management Systems by Mark L. Gillenson, Ph.D. College of Memphis Presentation by: Amita Goyal Chin, Ph.D. Virginia Commonwealth University John Wiley & Sons, Inc.

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Chapter Objectives Describe how unary and ternary connections are actualized in a social database. Clarify the idea of referential honesty. Depict how the referential trustworthiness limit, course, and set-to-invalid erase rules work in a social database.

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General Hardware Co. counting OFFICE

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General Hardware Co. counting OFFICE

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Unary One-to-Many Relationships A businessperson reports to precisely one deals chief, yet every sales representative who serves as a business administrator regularly has a few salespersons answering to him. There is a one-to-numerous relationship inside salespersons. Salesman (additionally a business supervisor) Salesperson

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Unary One-to-Many Relationships An unary relationship in light of the fact that there is one and only element sort included. A one-to-numerous in light of the fact that among the individual element events, that is, among the salespersons, a specific businessperson reports to one sales representative who is his business administrator, while a salesman who is a business supervisor may have a few salespersons answering to her.

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General Hardware Co. Sales representative Reporting Hierarchy

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One-to-Many Unary Relationship Requires the expansion of one segment to the connection speaking to the single element required in the unary relationship.

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Unary Many-to-Many Relationships An exceptional case, a case of which has come to be known as the bill of materials issue. Each element event can be identified with numerous different events. Item Product

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General Hardware Company\'s Product Set Tools and sets of instruments are sold. Numerous to-numerous nature of items.

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Modified Product Relation Product Numbers have been diminished to 2 digits for straightforwardness. Each individual unit thing and each arrangement of instruments has its own particular column in the connection in light of the fact that each thing and set is accessible available to be purchased.

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Unary Many-to-Many Relationship: New Relation Just as a double numerous to-numerous relationship requires the production of an extra connection in a social database, so does an unary numerous to-numerous relationship. The space of estimations of every segment is that of the Product Number segment of the PRODUCT connection.

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Ternary Relationships Involves three distinctive element sorts.

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General Hardware Co.: Ternary Relationship

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Ternary Relationship These new General Hardware Co. relations are all free with no remote keys in any of them. The SALES connection demonstrates how this ternary relationship is spoken to in a social database.

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Ternary Relationship The essential key of the extra connection (SALES) will be (in any event) the blend of the essential keys of the elements required in the relationship.

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Ternary Relationship Did businessperson 137 offer item 19440 to client 0839?

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Database Operations notwithstanding recovering information we should be set up to perform information upkeep operations, including: embeddings new records erasing existing records upgrading existing records

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Referential Integrity Revolves around the situation of attempting to allude to information in one connection in the database, in light of qualities in another connection.

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Referential Integrity - Record Deletion An issue emerges, e.g., in light of the fact that an erased record, a sales representative record, is on the "one side" of a one-to-numerous relationship.

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Referential Integrity - Insertion - if another record is embedded into the "one side" (SALESPERSON connection) of the one-to-numerous relationship, there is no issue. On the off chance that another client record is embedded into the "numerous side" (CUSTOMER connection) of the one-to-numerous relationship and it happens to incorporate a sales representative number that does not have a match in the SALESPERSON connection—that would bring about the same sort of issue as the cancellation illustration.

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Referential Integrity - Update Updating a remote key quality. For instance, a sales representative number in the CUSTOMER connection with another businessperson number that has no match in the SALESPERSON connection.

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DBMS & Referential Integrity Early social DBMSs did not give any control components to referential trustworthiness. Advanced social DBMSs give refined control components to referential respectability: Delete rules Insert rules Update rules

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Three Delete Rules Restrict Cascade Set-to-Null

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Delete Rule: Restrict If an endeavor is made to erase a record on the "one side" of the one-to-numerous relationship, the framework will disallow the erase to occur if there are any coordinating outside key qualities in the connection on the "numerous side."

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Delete Rule: Restrict If an endeavor is made to erase the record for businessperson 361 in the SALESPERSON connection, the framework won\'t allow the erasure to happen in light of the fact that the CUSTOMER connection records for clients 1525 and 1700 incorporate sales representative number 361 as a remote key worth.

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Delete Rule: Cascade If an endeavor is made to erase a record on the "one side" of the relationship, will that record be erased as well as the greater part of the records on the "numerous side" of the relationship that have a coordinating outside key worth will likewise be erased. The erasure will course from one connection to the next.

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Delete Rule: Cascade If an endeavor is made to erase the record for salesman 361 in the SALESPERSON connection, that sales representative record will be erased thus as well, consequently, will the records for clients 1525 and 1700 in the CUSTOMER connection since they have 361 as an outside key quality.

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Delete Rule: Set-to-Null If an endeavor is made to erase a record on the "one side" of the one-to-numerous relationship, that record will be erased and the coordinating remote key qualities in the records on the "numerous side" of the relationship will be changed to invalid.

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Delete Rule: Set-to-Null If an endeavor is made to erase the record for sales representative 361 in the SALESPERSON connection, that record will be erased, and the Salesperson Number characteristic qualities in the records for clients 1525 and 1700 in the CUSTOMER connection will have their Salesperson Number trait values changed from 361 to invalid.

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