Relational database schema

The main contents of the chapter consist of the following: Function M-files, syntax of function M-Files, comments, multiple input and output functions, relational model concepts, relational model constraints and relational database schemas, update operations and dealing with constraint violations.

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Bài giảng "Cơ sở dữ liệu - Chương 3: Mô hình dữ liệu quan hệ" cung cấp cho người đọc các kiến thức: Quá trình thiết kế CSDL, quan hệ (Relation), thuộc tính (Attribute), lược đồ (relation schema), kiểu dữ liệu và miền giá trị (Domain),... Mời các bạn cùng tham khảo nội dung chi tiết.

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Chapter 7 discusses how to design a relational database schema based on a conceptual schema design. This chapter presented a high-level view of the database design process, and in this chapter we focus on the logical database design or data model mapping step of database design. We present the procedures to create a relational schema from an Entity-Relationship (ER) or an Enhanced ER (EER) schema.

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Chapter 8 describes more advanced features of the SQL language standard for relational databases. In this chapter present more complex features of SQL retrieval queries, such as nested queries, joined tables, outer joins, aggregate functions, and grouping.

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Chapter 11 present the contents: Designing a set of relations, properties of relational decompositions, algorithms for relational database schema, multivalued dependencies and fourth normal form, join dependencies and fifth normal form, inclusion dependencies, other dependencies and normal forms.

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Relation Decomposition and Insufficiency of Normal Forms (cont.): Attribute preservation condition: Each attribute in R will appear in at least one relation schema Ri in the decomposition so that no attributes are “lost”. Another goal of decomposition is to have each individual relation Ri in the decomposition D be in BCNF or 3NF. Additional properties of decomposition are needed to prevent from generating spurious tuples

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Data Model: A set of concepts to describe the structure of a database, and certain constraints that the database should obey. Data Model Operations: Operations for specifying database retrievals and updates by referring to the concepts of the data model. Operations on the data model may include basic operations and user-defined operations.

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The minimum number of Cs that can be associated with one A is 1. I know this because the existence of the C to A relationship is mandatory. The maximum number of Cs that can be associated with one A is unlimited (or many). I know this because the cardinality of the C to A relationship is 1-M.

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For each weak entity type W in the ER schema with owner entity type E, create a relation R and include all simple attributes (or simple components of composite attributes) of W as attributes of R. In addition, include as foreign key attributes of R the primary key attribute(s) of the relation(s) that correspond to the owner entity type(s). The primary key of R is the combination of the primary key(s) of the owner(s) and the partial key of the weak entity type W, if any.

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Used to CREATE, DROP, and ALTER the descriptions of the tables (relations) of a database...

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[ Team LiB ] Recipe 2.1 Retrieving Hierarchical Data into a DataSet Problem You want to fill a DataSet with parent and related child data, even if the DataSet already has a schema that includes the relationship. Solution There are several techniques you can use to load parent and child data into a DataSet.

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Oracle object technology is a layer of abstraction built on Oracle relational technology. New object types can be created from any built-in database types and any previously created object types, object references, and collection types. Metadata for user-defined types is stored in a schema that is available to SQL, PL/SQL, Java, and other published interfaces

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