Syntax:
TRUNCATE(X,D)

Returns the number X, truncated to D decimal places. If D is 0, the
result has no decimal point or fractional part. D can be negative to
cause D digits left of the decimal point of the value X to become zero.
If X or D is NULL, the function returns NULL.

URL: https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html

