MEPX
Chapter 2 of 10All chapters
  1. 1Why a database
  2. 2Tables, rows and types
  3. 3Keys
  4. 4Relationships
  5. 5Normalisation
  6. 6Transactions
  7. 7Indexes
  8. 8When not to use tables
  9. 9Changing the schema
  10. 10Backups and growth

Chapter 2 of 10

Tables, rows and types

The basic shapes.

Choosing types

Every column has a type, and picking the right one is a form of validation. Dates in a date column can be compared and sorted; dates in a text column cannot be trusted at all.

  • Store money as a decimal or as integer minor units, never as a float.
  • Store timestamps in UTC and convert for display.

NOT NULL and defaults

Deciding which columns may be empty is a design decision, not a detail. Every nullable column is a branch someone has to handle for the life of the system.