Numeric literals are written as a sequence of digits from 0 to 9. Initial
zeros are ignored. A sign can always precede the digits, but it is optional
for positive numbers. In decimal numbers, the integer part and the decimal
part are divided with a dot (.).

If the integer part is zero, it can be omitted, but the literal must begin
with a dot.

The notation with exponent can be used. The exponent is preceded by an E or e
character. The exponent can be preceded by a sign and must be an integer. A
number N with an exponent part X, is calculated as N * POW(10, X).

In some cases, adding zeroes at the end of a decimal number can increment the
precision of the expression where the number is used. For example, PI() by
default returns a number with 6 decimal digits. But the PI()+0.0000000000
expression (with 10 zeroes) returns a number with 10 decimal digits.

Hexadecimal literals are interpreted as numbers when used in numeric contexts.

Examples
--------

10
+10
-10

All these literals are equivalent:

0.1
.1
+0.1
+.1

With exponents:

0.2E3 -- 0.2 * POW(10, 3) = 200
.2e3
.2e+2
1.1e-10 -- 0.00000000011
-1.1e10 -- -11000000000

URL: https://mariadb.com/kb/en/numeric-iterals/