Designing your database

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Aims and Learning ObjectivesBy the end of this document, you will be able to:

  • explain the three types of logical relationship that can be identified indatabase design and point out the only relationship that should be used in logical design;
  • explain how to resolve many-to-many relationships;
  • explain where primary and foreign keys must be located in any logical design;
  • capture data requirements from paper forms or spreadsheets;
  • draw simple data structure models with correctly-placed primary and foreign keys.



Why do I need to make plans before I start to build my database?

Too many databases fail to do what was planned because simple questions were not asked and simple tasks were not done beforehand. Poor planning results in timewasting throughout development and often leads to an unusable database. Yes, parts might work, but it could take longer to do the job using the database than it did to do it manually – and the database might provide less accurate results to boot.

Prerequisites

A clear understanding of what you want to get out of your database once it is completed. If you know what outputs you want, then you are more than half way toward knowing what inputs you need: and if you know what inputs you need, then you should have little trouble working out what tables your database needs. At which point, this document will fill in the gaps to help you design your database correctly.



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