vbsql學(xué)籍管理論文1英文文獻(xiàn)-文庫吧資料
2025-01-18 00:06本頁面
【正文】 eparation 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。 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。 last names. Data is retrieved from a table by filtering on both the row and the column. ６ 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. Note: Most of Scott39。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。s go over the basic ponents of a traditional relational database system and look at how a relational database is designed. Once you have a solid understanding of what rows, columns, tables, and relationships are, you39。 Along with information technique more and more thorough but extensive on the management of application, manage information system of the implement has been gradually mature on the the information system is a new academics which continuously develops, the whichever unit wants to exist to want adevelopment, highefficiencily internal activity anically the anization get up, have to build up adapting with oneself characteristics mutually of management information system. ５ This text introduced in the Visual under the environments the strategy of adoptionfrom top to bottom total programming, from bottom but last pplication development develop a process which manage information the shortage of analytical visitor management, established a valid a set of line a calculator a management the student39。然而，一旦設(shè)計(jì)進(jìn)入到實(shí)際的運(yùn)作，數(shù)據(jù)庫管理員就會(huì)很快讓設(shè)計(jì)者從理想回到現(xiàn)實(shí)中來。 一旦設(shè)計(jì)過程完成，下面將要建立實(shí)際的數(shù)據(jù)庫表。當(dāng)我們?cè)诨仡欔P(guān) 聯(lián)時(shí)，就會(huì)發(fā)現(xiàn)需要建立新的實(shí)體。這是實(shí)現(xiàn)列的使用，如右圖所示由工資水平實(shí)體所建立的工資水平表。而學(xué)生 _班級(jí)關(guān)系表中就
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