Essay About Structure Of Relational Database And Figure A

Structure of Relational Database
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Define the structure of relational database. and Relational database are one of the types of database that use tables to organize the data based on specific characteristics and group. The tables are formally-described so that we didn’t need to reorganize or copy back our data once we had key-in the data. In structured the tables, there are some rules and element that need to be emphasises such as foreign key, primary key, domain and referential integrity as data are subject to change in database. In addition, the link between the data and the data that are referred to are called relationship as they are connected through a common field. Primary key and foreign key related to each other as key in common field are call primary key and the one in referred field are called foreign key. So in the figure A the primary key is CategoryID in Categories but a foreign key in Products. As some data will be used again and again with difference criteria so to make it synchronized referential integrity was built. Referential integrity is when the data is satisfy with each other as the data in common field are exist in the referred one.  [pic 1]Figure A (one-to-many- relationship)     Besides that, there are three types of database that exist within relational database which is   one-to-many-relationship, one-to-one-relationship and many-to-many relationship. This relationship are differentiate by the link that are portrayed by ‘1’ and ‘∞’.’1’ means that the record will be only appeared once and ‘∞’ means that it can appeared many times. As an example in figure A,the record of CategoryID can only appeared once in Categories but the records in CategoryID in Products can appeared many times means that Figure A are one-to-many-relationship. On the other hand, one-to-one relationship will only have ‘1’ and many-to- many relationship will only have ‘∞’ in their link meaning that in one-to-one relationship the record only can appear once and vice versa for many-to- many as it can appeared numerous times as we can see in the figure B below.  [pic 2]Figure B(one-to-one- relationship)How data key-in into the database   When the structure of data has been recognize and the relationship has been created so the data can be key-in into the database.However, as database are using Database Management Systems(DBMs) such as Microsoft Access, there are certain point when we import data from other sources such as Microsoft Word,errors can occurs. So,we must make the format of the other sources match the format of our database.Besides using tables to insert a data, we can also using form as it is much easier and more accurate.