Premium

Numeric data type

Numerical data are divided into exact and approximate, integer and real. Bit values are a separate category.

Exact integers

TypeMemory sizeRange
TINYINT1 bytefrom -128 to 127 (from -27 to 27-1)
from 0 to 255 (from 0 to 28-1)
SMALLINT2 bytefrom -32768 to 32767 (from -215 to 215-1)
from 0 to 65535 (from 0 to 216-1)
MEDIUMINT3 bytefrom -223 to 223-1
from 0 to 224-1
INT
INTEGER
(aliases)		4 bytefrom -231 to 231-1
from 0 to 232-1
BIGINT8 bytefrom -263 to 263-1
from 0 to 264-1

Integers can be declared with the keyword UNSIGNED. In this case, the elements of this column it will not be possible to assign negative values, and the valid range, which takes on the type doubles. So, type TINYINT can take values from -128 to 127, and TINYINT UNSIGNED — from 0 to 255.

Exact real numbers

TypeRange
DEC[(M,D)]
DECIMAL[(M,D)]
(aliases)		Depends on M and D parameters

Type DECIMAL stores exact real values data. It is used when accuracy is critical. For example, when storing financial data.

Usage example:

MySQL
CREATE TABLE Users (
    ...
    salary DECIMAL(5,2)
);

This example declares that the salary column will store numbers, having a maximum of 5 digits, 2 of which are reserved for decimal part. That is, this column will store values in the range from -999.99 to 999.99.

The syntax DECIMAL is equivalent to DECIMAL(M) and DECIMAL(M,0). By default, the parameter M is 10.

The whole part and the part after the point are stored as 2 separate integers. On Based on this fact, the amount of memory consumed can be easily calculated. So for DECIMAL(5,2) the integer part contains 3 digits and takes 2 byte, part after the point have 2 digits - 1 byte is enough. Total for storage will be spent 3 byte.

Bit numbers

TypeMemory sizeRange
BIT[(M)]M bitFrom 1 to 64 bit, depend on the M parameter
BOOL
BOOLEAN
(aliases)		1 bitOr 0, or 1

Type BIT(M) stores a sequence of bits a given length. By default, the length is 8 bit. If assigned the value in a column of this type uses less than M bit, then zeros are padded on the left. For example, when trying to write the value b'101' to BIT(6) will eventually be stored b'000101'.

Approximate numbers

TypeMemory sizeRange
FLOAT[(M, D)]4 byteMinimum value ±1.17·10-39
Maximum value ±3.4·1038
REAL[(M, D)]
DOUBLE[(M, D)]
(aliases)		8 byteMinimum value ±2.22·10-308
Maximum value ±1.79·10308

Numeric floating point data types can also have a parameter UNSIGNED. As with integer types, this attribute prevents negative storage in the marked column values, but, unlike integer types, the maximum interval for column values remains the same.