XQuery/Ah-has
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(Redirected from XQuery/Ahhas)Redundancy in Expressions
[edit | edit source]let $r := if ($x = 1) then true() else false();
better as
let $r := ($x = 1)
and
for $p in (0 to string-length($arg1)) return $p
better as
(0 to string-length($arg1))
and
for $i in (1 to 5) return for $j in (11 to 15) return ($i, $j)
better as
for $i in (1 to 5), $j in (11 to 15) return ($i, $j)
OR
for $i in (1 to 5) for $j in (11 to 15) return ($i, $j)
all three return
(1 11 1 12 1 13 1 14 1 15 2 11 2 12 2 13...)
XPath predicates clearer and faster than where clauses
[edit | edit source]for $x in //Page where $x/heading = 1 return $x
better as
//Page[heading = 1]
Default values
[edit | edit source]if (exists($a)) then $a else "Default"
better as
($a,"Default") [1]
OR for a sequence of items
($list1, "Default"[empty($list1)])
OR another possible for a sequence
(<test/>,<test/>,<default/>)[not(position() = last() and not(last() = 1))]
any number of cascaded defaults can be handled this way.
compare with 'COALESCE' in SQL