Syntax:
INTERVAL(N,N1,N2,N3,...)

Returns 0 if N <= N1, 1 if N <= N2 and so on, or -1 if N is NULL. All
arguments are treated as integers. It is required that N1 <= N2 <= N3
<= ... <= Nn for this function to work correctly. This is because a
binary search is used (very fast).

URL: https://dev.mysql.com/doc/refman/8.0/en/comparison-operators.html

