Mark Rotteveel wrote: > While going over the language reference to do some manual fixes, I came > across the following caution (see > https://firebirdsql.org/file/documentation/reference_manuals/fblangref25-en/html/fblangref25-dml-select.html#fblangref25-dml-select-orderby-unions > > """ > Expressions whose calculation results are non-negative integers will be > interpreted as column position numbers and will cause an exception if > they fall outside the range from 1 to the number of columns. > > Example: > > SELECT > X, Y, NOTE > FROM PAIRS > ORDER BY X+Y DESC > > > * The number returned by a function or a procedure is unpredictable, > regardless of whether the sort order is defined by the expression itself > or by the column number > * Only non-negative integers are interpreted as column numbers > * An integer obtained by one-time evaluation of an expression or by > parameter substitution is saved as a constant, because this value > applies to all rows. > """ > > I just tested this in Firebird 2.5 and 1.5, and this is not actually the > case (and I would be surprised if it ever has been the case). The value > of an expression itself is used to sort. As far as I'm aware only > literal or parenthesized literal values can be used to identify column > positions. > > Any objections if I just remove this caution in the new version?
No, please correct this. I sometimes use expressions for ordering levels, e.g. with IIF or DECODE constructs that return, say, the numbers 1, 2 and 3, and they do the expected thing in Fb 2.5 and 3, i.e. they sort by the numerical value returned, not by the contents of column 1, 2 or 3. It would be silly anyway, because the value of X+Y may vary wildly across rows, so which one would determine the column number to sort by? Maybe what they're (trying to) say is true for constant expressions and/or expressions involving only constants and local variables in PSQL. Paul Vinkenoog _______________________________________________ Firebird-docs mailing list Firebird-docs@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/firebird-docs
