When a data field is compared to a literal string that is shorter than the data field, the string is padded. Character strings are padded with blanks, for example:
NULLIF (1:4)=" "
This example compares the data in position 1:4 with 4 blanks. If position 1:4 contains 4 blanks, then the clause evaluates as true.
Hexadecimal strings are padded with hexadecimal zeros, as in the following clause:
NULLIF (1:4)=X'FF'
This clause compares position 1:4 to hexadecimal 'FF000000'.