Design

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compare

The compare function in XQuery is used to compare two strings using a specified collation. This function can help determine the order of strings, for example, sorting based on a defined collation.

Syntax

fn:compare(comparand1, comparand2, collation)

The following table describes the argument for this command:

Argument	Required/Optional	Description
comparand1	Required	The first string to be compared. This can be a valid string or empty-sequence() .
comparand2	Required	The second string to be compared. This can also be a valid string or empty-sequence() .
collation	Optional	A string that specifies the collation URI to be used for the comparison. If omitted, the default collation is used. The collation affects how string comparison is done, taking locale-specific rules into account.

Return Value

Returns a negative integer if

$comparand1

is less than

$comparand2

Returns zero if the strings are equal.

Returns a positive integer if

$comparand1

is greater than

$comparand2

Returns

empty-sequence()

if either input is

empty-sequence()

Examples

The following table lists some sample values and return values:

SAMPLE FUNCTION	OUTPUT
fn:compare('a', 'b')	-1
fn:compare('a', 'a')	0
fn:compare('b', 'a')	1
fn:compare('ab', 'abc')	-1
fn:compare('a', 'B')	1 This shows that when using the simple code point collation, a lowercase a comes after an uppercase B .
fn:compare(upper-case('a'), upper-case('B'))	-1
fn:compare('a', ())	()
fn:compare('a', 'b', 'FOO')	Error FOCH0002
fn:compare((), ())	()