- The smaller the query the better (usually)
- Simple is good:
- INT is faster than CHAR
- Dates and times are better when used with built-in types instead of VARCHAR
- IP are better stored as INT (personally I don't like this, but ...)
- Avoid NULL:
- It uses more space and special features to store and compare null fields.
- Use 0 or other INT instead.
- It's specially useful for indexing as well