Simple question. I have tried searching on Google and after about 6 searches, I figured it would be faster here.
How big is an int in SQL?
-- table creation statement.
intcolumn INT(N) NOT NULL,
-- more table creation statement.
How big is that INT(N) element? What's its range? Is it 2^N or is it N Bytes long? (2 ^ 8N)? Or even something else I have no idea about?
It depends on the database. MySQL has an extension where INT(N) means an INT with a display width of 4 decimal digits. This information is maintained in the metadata. The INT itself is still 4 bytes, and values 10000 and greater can be stored (and probably displayed, but this depends how the application uses the result set).
That depends entirely on the database engine you are using. But I believe most engines consider the INT/INTEGER types to be 32-bit. Most engines will let you specify the signedness.
The actual N only specifies the number of digits. So an unsigned INT(3) has the range of 0-999.
来源：https://stackoverflow.com/questions/4151259/whats-the-size-of-an-sql-intn