From: Ann W. Harrison
Date: February 18 2009 5:17pm
Subject: Re: Patch for bug#42208
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Here's what the standard (bless it's scaly two-chambered heart) has
to say about binary string comparisons.

4.3.1 Introduction to binary strings
     A binary string is a sequence of octets that does not have
     either a character set or collation associated with it.

     A binary string type is described by a binary string type
     descriptor. A binary string type descriptor contains:

     — The name of the data type (BINARY, BINARY VARYING, or BINARY
       LARGE OBJECT).

     — The length or maximum length in octets of the binary string
       type

     A binary string is assignable only to sites of binary string
     type. If a store assignment would result in the loss of non-zero
     octets due to truncation, then an exception condition is raised.
     If a retrieval assignment would result in the loss of octets due
     to truncation, then a warning condition is raised.

4.3.2 Binary string comparison
     All binary string values are comparable. When binary large
     object string values are compared, they shall have exactly
     the same length (in octets) to be considered equal. Binary
     large object string values can be compared only for equality.

     For binary string values other than binary large object
     string values, it is implementation-defined whether trailing
     X'00's are considered significant when comparing two binary
     string values that are otherwise equivalent.


So, in a word, the standard writers chose to punt on whether a
varbinary 0x00 ix the same as 0x0000 when it's a varbinary, but
say that they aren't equal if they're blobs.

("punt" - expression from American football, meaning give the ball
a good hard kick and let the other team deal with it.  Has nothing
to do with "punt" the square boat propelled by poles on English
rivers.)

So the next question is "who is the implementer here?"

Cheers,

Ann