VARCHAR disadvantages:
- uses 2 extra bytes to store the length
- needs a little extra effort when storing and manipulating length of VARCHAR -> may affect efficiency
General Rule:
- Use CHAR if average length of field is more than 6 bytes to save space
- if average length of field is less than 6 bytes, there will be no storage savings for using char
- Use varchar for columns with more that 30 characters (can be shorter for others)
