DECIMAL[(M[,D])] [UNSIGNED] [ZEROFILL]

A packed "exact" fixed-point number. M is the total number of digits
(the precision) and D is the number of digits after the decimal point
(the scale). The decimal point and (for negative numbers) the - sign
are not counted in M. If D is 0, values have no decimal point or
fractional part. The maximum number of digits (M) for DECIMAL is 65.
The maximum number of supported decimals (D) is 30. If D is omitted,
the default is 0. If M is omitted, the default is 10. (There is also a
limit on how long the text of DECIMAL literals can be; see
https://dev.mysql.com/doc/refman/8.0/en/precision-math-expressions.html
.)

UNSIGNED, if specified, disallows negative values. As of MySQL 8.0.17,
the UNSIGNED attribute is deprecated for columns of type DECIMAL (and
any synonyms); you should expect support for it to be removed in a
future version of MySQL. Consider using a simple CHECK constraint
instead for such columns.

All basic calculations (+, -, *, /) with DECIMAL columns are done with
a precision of 65 digits.

URL: https://dev.mysql.com/doc/refman/8.0/en/numeric-type-syntax.html

