Question : Think of the small database we used in our lab exercise - Products and Suppliers. Briefly describe how this database observes any two of the four design principles outlined above.Answer : Primary Key
The primary key is most essential to identify the suppliers and products classification. It is a column or columns that must be unique in a table. But beyond that, the primary key is not just unique values, but unique values for like items. Database design skills begin with identifying the kinds of things that must be tracked, putting each into a table, and assigning the primary keys to those tables.
Relational Database
The relation is the primary unit of storage in a relational database, which is a two-dimensional table. A relational database can contain one or more of these tables. Each table consists of a unique set of rows and columns. A single record is stored in a table as a row, also known as a tuple. Attributes of the data are defined in columns, or fields, in the table. The characteristics of the data, or the column, relates one record to another. Each column has a unique name and the content within it must be of the same type.
You have summarized the principles of relational database design nicely.
回覆刪除Our small database has two tables - for Products and Suppliers. This shows that our data has been organized by Subject, because each table is only concerned with one subject.
The foreign key "Supplier Number" allows us to link or combine related records from the two tables.
We also used the Report Wizard to retrieve and combine data from the tables in a more meaningful way (e.g. selecting only certain records and fields, sorting/grouping records, adding totals).