A while ago I was quite surprised to see that the following query returns 1 instead of 0:

SELECT COUNT(*) WHERE N'Tim' = N'Tim '; -- notice the trailing space


Apparently this is just standard behaviour. Here is an extract from sql1992.txt (Section 8.2 Paragraph 3):

3) The comparison of two character strings is determined as fol-
lows:

a) If the length in characters of X is not equal to the length
in characters of Y, then the shorter string is effectively
replaced, for the purposes of comparison, with a copy of
itself that has been extended to the length of the longer
string by concatenation on the right of one or more pad char-
acters, where the pad character is chosen based on CS. If
CS has the NO PAD attribute, then the pad character is an
implementation-dependent character different from any char-
acter in the character set of X and Y that collates less
than any string under CS. Otherwise, the pad character is a
<space>.

b) The result of the comparison of X and Y is given by the col-
lating sequence CS.

c) Depending on the collating sequence, two strings may com-
pare as equal even if they are of different lengths or con-
tain different sequences of characters. When the operations
MAX, MIN, DISTINCT, references to a grouping column, and the
UNION, EXCEPT, and INTERSECT operators refer to character
strings, the specific value selected by these operations from
a set of such equal values is implementation-dependent.