外文翻譯---關(guān)系數(shù)據(jù)庫的結(jié)構(gòu)-其他專業(yè)-文庫吧資料
2025-01-27 09:22本頁面
【正文】 can maintain entities, their attributes, and their relationships. In general, an entity corresponds to a table in the database, and the attributes of the entity correspond to columns of the table. Data Modeling:A process of defining the entities, attributes, and relationships between the entities in preparation for creating the physical database. The datamodeling process involves defining the entities, defining the relationships between those entities, and then defining the attributes for each of the entities. Once a cycle is plete, it is repeated as many times as necessary to ensure that the designer is capturing what is important enough to go into the database. Let39。s assume for the moment that the majority of the database design is pleted and some tables need to be implemented. Scott creates the EMP table to hold the basic employee information, and it looks something like this: Notice that some fields in the Commission （ COMM） and Manager （ MGR） columns do not contain a value。 last names. Data is retrieved from a table by filtering on both the row and the column. Primary Keys, Datatypes, and Foreign Keys The examples throughout this article will focus on the hypothetical work of Scott Smith, database developer and entrepreneur. He just started a new widget pany and wants to implement a few of the basic business functions using the relational database to manage his Human Resources （ HR） department. Relation: A twodimensional structure used to hold related information, also known as a table. Row:A group of one or more data elements in a database table that describes a person, place, or thing. Column:The ponent of a database table that contains all of the data of the same name and type across all rows. You39。ll be well on your way to leveraging the power of a relational database. Tables, Row, and Columns A table in a relational database, alternatively known as a relation, is a twodimensional structure used to hold related information. A database consists of one or more related tables. A row in a table is a collection or instance of one thing, such as one employee or one line item on an invoice. A column contains all the information of a single type, and the piece of data at the intersection of a row and a column, a field, is the smallest piece of information that can be retrieved with the database39。 附件：外文資料原文 Structure of the Relational database The relational model is the basis for any relational database management system （ RDBMS） .A relational model has three core ponents: a collection of objects or relations, operators that act on the objects or relations, and data integrity methods. In other words, it has a place to store the data, a way to create and retrieve the data, and a way to make sure that the data is lo
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