Impressive, just one comment:
> 5. I need in advice: if subquery introduced with NOT IN doesn't return
> any tuples then qualification is failed, yes ?
I think this is backwards. Consider the following statements:
"1 not in (1,2)" FALSE
"1 not in (2)" TRUE
"1 not in ()" ?
I would tend to think that the ? should be TRUE. I.E. every value
qualifies as not in an empty list of tuples. The second item was
true, so why should removing the 2 from the list make the statement
false?
Ocie Mitchell
