# XQuery/Ah-has

< XQuery

### Redundancy in ExpressionsEdit

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 clausesEdit

for $x in //Page where $x/heading = 1 return $x

better as

//Page[heading = 1]

### Default valuesEdit

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