inequality

Which of the two (semantically equivalent) ways is preferable to test for inequality? 'foo' != 'bar' (exclamation mark and equals sign) 'foo' <> 'bar' (less than and greater than chevron symbols together) The MySQL documentation clearly indicates that there is no difference between them and yet some people seem to be attached to only doing it one way or the other. Maybe this is just another pointless vi vs. emacs debate but when other people are reading your code (and therefore your queries), it's useful to maintain some consistency. <> looks a lot like <=> which is a very underused operator

I'm aware that app engine has the restriction of "Inequality Filters Are Allowed On One Property Only" as described here: http://code.google.com/appengine/docs/python/datastore/queriesandindexes.html#Introducing_Indexes However is there some way to essentially run two filters, or is this simply not possible? For instance, if I had an entity kind that simply had an X and Y coordinate, and I wanted all entities that are within a certain range of X1 to X2 and Y1 to Y2, is there some way to query for all entities from X1 to X2 sorted by their Y values and then easily grab the relevant ones between

I've just come across this in a WHERE clause: AND NOT (t.id = @id) How does this compare with: AND t.id != @id Or with: AND t.id <> @id I'd always write the latter myself, but clearly someone else thinks differently. Is one going to perform any better than the other? I know that using <> or != is going to bust any hopes for using an index that I might have had, but surely the first approach above will suffer the same problem? SQLMenace These 3 will get the same exact execution plan declare @id varchar(40) select @id = '172-32-1176' select * from authors where au_id <> @id select * from authors

What is the best method for comparing IEEE floats and doubles for equality? I have heard of several methods, but I wanted to see what the community thought. The best approach I think is to compare ULPs . bool is_nan(float f) { return (*reinterpret_cast<unsigned __int32*>(&f) & 0x7f800000) == 0x7f800000 && (*reinterpret_cast<unsigned __int32*>(&f) & 0x007fffff) != 0; } bool is_finite(float f) { return (*reinterpret_cast<unsigned __int32*>(&f) & 0x7f800000) != 0x7f800000; } // if this symbol is defined, NaNs are never equal to anything (as is normal in IEEE floating point) // if this symbol is