What's the difference between VARCHAR and CHAR?

Question

What's the difference between VARCHAR and CHAR in MySQL?

I am trying to store MD5 hashes.

Answer 1

VARCHAR is variable-length.

CHAR is fixed length.

If your content is a fixed size, you'll get better performance with CHAR.

Answer 2

A CHAR(x) column can only have exactly x characters.
A VARCHAR(x) column can have up to x characters.

Since your MD5 hashes will always be the same size, you should probably use a CHAR.

However, you shouldn't be using MD5 in the first place; it has known weaknesses.
Use SHA2 instead.
If you're hashing passwords, you should use bcrypt.

Answer 3

CHAR is fixed length and VARCHAR is variable length. CHAR always uses the same amount of storage space per entry, while VARCHAR only uses the amount necessary to store the actual text.

Answer 4

This answer from www.mssqlcity.com seems to sum it up nicely:

The char is a fixed-length character data type, the varchar is a variable-length character data type.

Because char is a fixed-length data type, the storage size of the char value is equal to the maximum size for this column. Because varchar is a variable-length data type, the storage size of the varchar value is the actual length of the data entered, not the maximum size for this column.

You can use char when the data entries in a column are expected to be the same size. You can use varchar when the data entries in a column are expected to vary considerably in size.

Answer 5

CHAR is a fixed length field; VARCHAR is a variable length field. If you are storing strings with a wildly variable length such as names, then use a VARCHAR, if the length is always the same, then use a CHAR because it is slightly more size-efficient, and also slightly faster.

Answer 6

Here's what it says in the MySQL Manual.

Answer 7

In most RDBMSs today, they are synonyms. However for those systems that still have a distinction, a CHAR field is stored as a fixed-width column. If you define it as CHAR(10), then 10 characters are written to the table, where "padding" (typically spaces) is used to fill in any space that the data does not use up. For example, saving "bob" would be saved as ("bob"+7 spaces). A VARCHAR (variable character) column is meant to store data without wasting the extra space that a CHAR column does.

As always, Wikipedia speaks louder.

Answer 8

CHAR Vs VARCHAR

CHAR is used for Fixed Length Size Variable
VARCHAR is used for Variable Length Size Variable.

E.g.

Create table temp
(City CHAR(10),
Street VARCHAR(10));

Insert into temp
values('Pune','Oxford');

select length(city), length(street) from temp;

Output will be

length(City)          Length(street)
10                    6

Conclusion: To use storage space efficiently must use VARCHAR Instead CHAR if variable length is variable