In this lesson, you have learned about database design and the important role it plays in creating a good data management system. Keep these points in mind when you design your databases:
•Relational databases store data in tables. Tables contain data about a single subject and consist of columns, which represent the facts about the subject. A single row of data pertains to a single instance in that table; for example, employee number 100 will reference only one employee in the Employee table.
•Key columns are used to ensure the accuracy of your data and improve the speed of your database's performance. Key columns uniquely identify a single row of data in a table and establish common or linking columns with other tables.
•There are three types of relationships among tables: one-to-one, one-to-many, and many-to-many.
To check your knowledge, try answering the following questions:
| 1. | What do objects become in a database model? |
| 2. | What do facts become in a database model? |
| 3. | What is a key? |
| 4. | When a one-to-many relationship exists between two tables, from which table do you take the key and place it in the other table to provide the link? |
| (a) Take primary key from the table on the one side and place it in the table on the many side. |
| (b) Take primary key from the table on the many side and place it in the table on the one side. |
| 5. | What effect does poor database design have on a database? |
| 6. | How many rows should you have in the Employee table for each employee? |
| 7. | In a well designed database can tables contain data about multiple subjects? (Yes- No) |
