數(shù)據(jù)庫外文翻譯---關系數(shù)據(jù)庫的結構-數(shù)據(jù)庫-全文預覽
【正文】 dentifies all of the entities within the scope of the database entities are the persons, places, or things that are important to the anization and need to be tracked in the database. Entities will most likely translate neatly to database tables. For example, for the first version of Scott39。ll learn about database design in the following sections, but let39。s query language. For example, a table with information about employees might have a column called LAST_NAME that contains all of the employees39。 譯文題目： 關系數(shù)據(jù)庫的結構 2021 年 12 月 05 日 原文 ： Structure of the Relational database — 《 Database System Concepts》 Part1: Relational Databases 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 logically consistent. A relational database uses relations, or twodimensional tables, to store the information needed to support a business. Let39。t confuse a relation with relationships. A relation is essentially a table, and a relationship is a way to correlate, join, or associate two 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。 original hire date in the new database. 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。t report to anyone. Field:The smallest piece of information that can be retrieved by the database query language. A field is found at the intersection of a row and a column in a database table. On the other hand, none of the fields in the Employee Number (EMPNO) column are blank. The pany always wants to assign an employee number to an employee, and that number must be different for each employee. One of the features of a relational database is that it can ensure that a value is entered into this column and that it is unique. The EMPNO column, in this case, is the primary key of the table. Primary Key:A column (or columns) in a table that makes the row in the table distinguishable from every other row in the same table. Notice the different datatypes that are stored in the EMP table: numeric values, character or alphabetic values, and date values. As you might suspect, the DEPTNO column contains th
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