An UpdateIfExpr is a conditional expression for use in
an update expression. If the expression following the if keyword
evaluates to true, the update expression following the then
keyword is applied, otherwise the update expression following the
else keyword is applied.
If the then branch and/or the else branch does
not require any update operations, an empty pair of parentheses should be
used.
Note that the else clause is mandatory.
Insert an attribute, if it does not exist yet, otherwise replace the
existing attribute, if its value is less then 100. This query contains two
UpdateIfExpr constructs, where the second one occurs in the
else branch of the first:
update
for $book in input()/bib/book
do
if (empty($book/@year)) then
insert attribute year {year-from-date(current-date())}
into $book
else if ($book/@year < 100) then
replace $book/@year
with attribute year {1900 + $book/@year}
else
()
The following construct(s) refer to this construct: