Good database design plans the structure before any data is added. This unit covers the three schema levels, entity relationship diagrams (ERDs), the data types used in tables, and how to normalize a database to third normal form to remove anomalies.
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Database schema: three levels
A schema is a blueprint of the database that describes its structure but holds no actual data.
The conceptual schema shows the entities and the relationships between them (least detailed) and is seen by both users and developers.
The logical schema adds the attributes for each entity, including the primary keys and foreign keys.
The physical schema is the most detailed: it adds the data types and key links used to actually set up the database.
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1. Which database schema shows the entities and the relationships between them, but does not include attributes, data types or constraints?
2. A table is already in first normal form. Removing partial key dependencies (attributes that rely on only part of a composite key) moves it into which normal form?
3. Why might a developer deliberately denormalize a database that has already been normalized to 3NF?
4. A developer needs to store a ticket price such as 34.99 so that calculations can later be performed on it. Which MySQL data type is most suitable?
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