SQL: Using NULL values vs. default values

by

I don’t know why you’re even trying to compare these to cases. null means that some column is empty/has no value, while default value gives a column some value when we don’t set it directly in query.

Maybe some example will be better explanation. Let’s say we’ve member table. Each member has an ID and username. Optional he might has an e-mail address (but he doesn’t have to). Also each member has a postCount column (which is increased every time user write a post). So e-mail column can have a null value (because e-mail is optional), while postCount column is NOT NULL but has default value 0 (because when we create a new member he doesn’t have any posts).

More Related Contents:

  1. How to implement a many-to-many relationship in PostgreSQL?
  2. How to create multiple one to one’s
  3. What are best practices for multi-language database design? [closed]
  4. Strings as Primary Keys in SQL Database [closed]
  5. Are soft deletes a good idea? [duplicate]
  6. Database Design for Revisions?
  7. A beginner’s guide to SQL database design [closed]
  8. Physical vs. logical (hard vs. soft) delete of database record? [closed]
  9. Storing money in a decimal column – what precision and scale? [closed]
  10. single fixed table with multiple columns vs flexible abstract tables
  11. Address standardization within a database
  12. Primary key or Unique index?
  13. Does MS Access support “CASE WHEN” clause if connect with ODBC?
  14. How to design a database for User Defined Fields?
  15. Composite Primary key vs additional “ID” column?
  16. Database EAV Pros/Cons and Alternatives
  17. Max length for client ip address [duplicate]
  18. Name database design notation you prefer and why?
  19. MySQL – how to front pad zip code with “0”?
  20. Use email address as primary key?
  21. Composite Primary Keys : Good or Bad?
  22. How can I implement SQL INTERSECT and MINUS operations in MS Access
  23. SQL ON DELETE CASCADE, Which Way Does the Deletion Occur?
  24. Lightweight SQL database which doesn’t require installation [closed]
  25. What does ON [PRIMARY] mean?
  26. What is the best way to implement soft deletion?
  27. Relational Data Model for Double-Entry Accounting
  28. Temporal database design, with a twist (live vs draft rows)
  29. Historical / auditable database
  30. Single or multiple databases

Leave a Comment