Design

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substring

The substring function in XQuery extracts a portion of a string based on specified start and optional length parameters. It is useful for string manipulation tasks where specific parts of a string need to be isolated and processed.

Syntax

fn:substring(sourceString, startingLoc, length)

The following table describes the argument for this command:

Argument	Required/Optional	Description
sourceString	Required	The string from which the substring will be extracted. If the argument is an empty sequence ( () ), it is treated as an empty string.
startingLoc	Required	The position within the source string where the substring begins. Position indexing starts at 1. If this number is less than 1, the start is considered from the first character.
length	Optional	The number of characters to include in the substring. If omitted, the substring extends to the end of the source string.

Return Value

Returns the portion of the value of

$sourceString

beginning at the position indicated by the value of

$startingLoc

and continuing for the number of characters indicated by the value of

$length

. The characters returned do not extend beyond

$sourceString

$startingLoc

is zero or negative, only those characters in positions greater than zero are returned.

If the start position is beyond the end of the string, it returns an empty string.

Examples

The following table lists some sample values and return values:

SAMPLE FUNCTION	OUTPUT
fn:substring('query', 1)	query
fn:substring('query', 3)	ery
fn:substring('query', 1, 1)	q
fn:substring('query', 2, 3)	uer
fn:substring('query', 2, 850)	uery
fn:substring('query', 6, 2)	zero-length string
fn:substring('query', -2)	query
fn:substring('query', -2, 5)	qu
fn:substring('query', 1, 0)	zero-length string
fn:substring('', 1)	zero-length string
fn:substring((), 1)	zero-length string
fn:substring("Example", 0)	"Example"
fn:substring("Short", 10)	""