What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?

Question

What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?

In what cases should these be used?

Answer 1

They take up different amounts of space and they have different ranges of acceptable values.

Here are the sizes and ranges of values for SQL Server, other RDBMSes have similar documentation:

• MySQL
• Postgres
• Oracle (they just have a NUMBER datatype really)
• DB2

Turns out they all use the same specification (with a few minor exceptions noted below) but support various combinations of those types (Oracle not included because it has just a NUMBER datatype, see the above link):

             | SQL Server    MySQL   Postgres    DB2
---------------------------------------------------
tinyint      |     X           X                
smallint     |     X           X         X        X
mediumint    |                 X
int/integer  |     X           X         X        X 
bigint       |     X           X         X        X

And they support the same value ranges (with one exception below) and all have the same storage requirements:

            | Bytes    Range (signed)                               Range (unsigned)
--------------------------------------------------------------------------------------------
tinyint     | 1 byte   -128 to 127                                  0 to 255
smallint    | 2 bytes  -32768 to 32767                              0 to 65535
mediumint   | 3 bytes  -8388608 to 8388607                          0 to 16777215
int/integer | 4 bytes  -2147483648 to 2147483647                    0 to 4294967295
bigint      | 8 bytes  -9223372036854775808 to 9223372036854775807  0 to 18446744073709551615 

The "unsigned" types are only available in MySQL, and the rest just use the signed ranges, with one notable exception: tinyint in SQL Server is unsigned and has a value range of 0 to 255