XQuery FLWOR

XQuery FLWOR Expressions

---

What is FLWOR?

FLWOR (pronounced "flower") is an acronym for "For, Let, Where, Order by, Return".

• For - selects a sequence of nodes
• Let - binds a sequence to a variable
• Where - filters the nodes
• Order by - sorts the nodes
• Return - what to return (gets evaluated once for every node)

---

The XML Example Document

We will use the "books.xml" document in the examples below (same XML file as in the previous chapter).
View the "books.xml" file in your browser.

---

How to Select Nodes From "books.xml" With FLWOR

Look at the following path expression:

doc("books.xml")/bookstore/book[price>30]/title

The expression above will select all the title elements under the book elements that are under the bookstore element that have a price element with a value that is higher than 30.
The following FLWOR expression will select exactly the same as the path expression above:

for $x in doc("books.xml")/bookstore/book
where $x/price>30
return $x/title

The result will be:

<title lang="en">XQuery Kick Start</title>
<title lang="en">Learning XML</title>

With FLWOR you can sort the result:

for $x in doc("books.xml")/bookstore/book
where $x/price>30
order by $x/title
return $x/title

The for clause selects all book elements under the bookstore element into a variable called $x.
The where clause selects only book elements with a price element with a value greater than 30.
The order by clause defines the sort-order. Will be sort by the title element.
The return clause specifies what should be returned. Here it returns the title elements.
The result of the XQuery expression above will be:

<title lang="en">Learning XML</title>
<title lang="en">XQuery Kick Start</title>

---