IBM Version 5 manual FLWRFOR, LET, Where and Return clauses expression

<job> $j </job> </emp>

Generate an element with a computed name, containing nested elements named <description> and <price>:

<$tagname>

<description> $d </description> , <price> $p </price>

</$tagname>

In this example, the tagname, with its end-tag itself is a variable.

FLWR(“FOR, LET, WHERE and RETURN clauses”) expression

A FLWR expression binds values to and more variables, and then uses these variables to construct a result. For the following example, the XML file would follow the structure shown:

<book> <title>...</title> <author>.....</author>

<author>....</author>

<publisher>...</publisher> <price>.......<price>

<year>....<year>

</book>

List the titles of books published by Morgan Kaufmann in 1998:

FOR $b IN document("bib.xml")//book

WHERE $b/publisher = "Morgan Kaufmann"

AND $b/year = "1998"

RETURN $b/title

List each publisher and the average price of its books:

FOR $p IN distinct(document("bib.xml")//publisher) LET $a := avg(document("bib.xml")

/book[publisher = $p]/price)

RETURN <publisher>

<name> $p/text() </name> , <avgprice> $a </avgprice>

</publisher>

Conditional expressions (IF THEN ELSE)

Conditional expressions are used when the information returned from a query depends on some condition.

Make a list of holdings, ordered by title. For journals, include the editor; and for all

Chapter 2. Technologies in XML 43