Name

XMLFOREST — Produces a forest of XML elements

Synopsis

XMLFOREST ( string_expr1 [AS alias1] varchar ,
  string_expr2 [AS alias2] varchar ,
  ... ,
  string_exprN [AS aliasN] varchar );
 

Description

XMLFOREST produces a forest of XML elements from the given list of arguments. The arguments may be string expressions with optional aliases. If string expression is a column name, then you can omit the AS clause, and Virtuoso uses the partially escaped form of the column name as the name of the enclosing tag. If the expression evaluates to NULL, then no element is created for that expression. If none of the element is created, then the function returns NULL.

Parameters

string_exprI [AS aliasI]

string value; AS clause is mandatory if the argument is not a column name but an expression of some other sort.

Errors

Table 24.129. Errors signalled by XMLFOREST

SQLState Error Code Error Text Description
37000 SQ074 The special SQL function has invalid argument An argument is neither a column name nor an expression with an alias.

Examples

Example 24.503. XMLFOREST() with five parameters.

The following example produces five (or four) elements ('FName', 'LName', 'str', 'Title', and 'Region' - if there is a value) from the string expressions 'FirstName', 'LastName', 'string', 'Title', and 'Region', concatenates the elements produced for each employee, and produces one row for each employee in the result set.

select XMLFOREST (
  "FirstName" as "FName", "LastName" as "LName",
  'string' as "str", "Title", "Region" )
from "Demo"."demo"."Employees";
callret
VARCHAR
_______________________________________________________________________________

<FName>Nancy</FName>
<LName>Davolio</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region>WA</Region>

. . .

<FName>Anne</FName>
<LName>Dodsworth</LName>
<str>string</str>
<Title>Sales Representative</Title>

9 Rows.
       

The following example always produces five elements: empty 'Region' element is created for NULL values. Note the difference in the last rows of this and the previous query results:

select XMLFOREST (
  "FirstName" as "FName", "LastName" as "LName",
  'string' as "str", "Title", coalesce ("Region", '') as "Region")
from "Demo"."demo"."Employees";
callret
VARCHAR
_______________________________________________________________________________

<FName>Nancy</FName>
<LName>Davolio</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region>WA</Region>

. . .

<FName>Anne</FName>
<LName>Dodsworth</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region></Region>

9 Rows.