Re: bug in substring???

"scott.marlowe" <scott.marlowe@ihs.com> writes:
> thanks.  I just got done looking up the SQL explanation, and I think my 
> head exploded.  Thanks for the heads up.

The formal definition seems unnecessarily complicated :-(, but the spec
authors' intent is reasonably clear from this paragraph in the
"Concepts" section of SQL92:
        <character substring function> is a triadic function, SUBSTRING,        that returns a string extracted from a
givenstring according        to a given numeric starting position and a given numeric length.        Truncation occurs
whenthe implied starting and ending positions        are not both within the given string.
 

In other words, they consider that a zero or negative start position
should be truncated back to the actual start position (1) in much the
same way that a too-large length specification would be truncated to
match the actual end position.

AFAICT the only case in which SUBSTRING is supposed to raise an error is
when you specify a negative length.
        regards, tom lane