What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?
In what cases should these be used?
解决方案
They take up different amounts of space and they have different ranges of acceptable values.
Oracle (they just have a NUMBER datatype really)
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:
tinyint: 1 byte, -128 to +127 / 0 to 255 (unsigned)
smallint: 2 bytes, -32,768 to +32,767 / 0 to 65,535 (unsigned)
mediumint: 3 bytes, -8,388,608 to 8,388,607 / 0 to 16,777,215 (unsigned)
int/integer: 4 bytes, -2,147,483,648 to +2,147,483,647 / 0 to 4,294,967,295 (unsigned)
bigint: 8 bytes, -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 / 0 to 18,446,744,073,709,551,615 (unsigned)
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
