I can think of a badly designed database interface. All SQL databases handle NULL as a special value, that cannot be compared by equality. But if you want compa

I can think of a badly designed database interface. All SQL databases handle NULL as a special value, that cannot be compared by equality. But if you want compare the return value of a sql prompt in some language you can make a fallacy like: sqlstring = "SELECT 1 = NULL;" returnValue = callDB(sqlstring) if returnValue == "NULL" // here you go... end A solution would be to let the database handle NULL-values: sqlstring = "SELECT 1 IS NULL;"