Syntax:
RPAD(str,len,padstr)

Returns the string str, right-padded with the string padstr to a length
of len characters. If str is longer than len, the return value is
shortened to len characters. If str, padstr, or len is NULL, the
function returns NULL.

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

