what’s the difference between `CHAR` and `VARCHAR` in database

content

for varchar(50),

a record has:
- a length prefix (usually 1 byte)
- the actual string data
when a string is an empty string ''
- it has a length prefix to indicate its length is 0 (1 byte)
- and the actual string data is 0 (0 byte)
- total space taken is 1 byte
when a string is full length (50)
- length prefix indicating its length is 50
- actual string data (1 character is 1 byte, 50 characters are 50 bytes)
- total space taken is 50 bytes

for char(50),