Substrings

Three functions are available to return part of a string. The substring function returns a substring based on a starting position (starting at 1 not 0) and optionally a length. For example:

substring("query", 2, 3)

returns the string uer. If no length is specified, the function returns the rest of the string. For example:

substring("query", 2)

returns uery.

The substring-before function returns all the characters of a string that occur before the first occurrence of another specified string. The substring-after function returns all the characters of a string that occur after the first occurrence of another specified string. Table 17-4 shows examples of the substring functions.

USEFUL FUNCTION: substring-after-last

If you want the substring that appears after the last occurrence of the specified string, you can use the substring-after-last function, shown here:

declare namespace functx = "http://www.functx.com";
declare function functx:substring-after-last
($string as xs:string?, $delim as xs:string) as xs:string?
 {
   if (contains ($string, $delim))
   then functx:substring-after-last(substring-after($string, $delim), $delim)
   else $string
 };

For example, calling this function with:

functx:substring-after-last("2006-05-03", "-")

will return 03. This function uses recursion to call the substring-after function repeatedly until the string no longer contains the search characters.

Table 17-4. Examples of the substring functions

Example

Return value

substring("query", 2, 3)

uer

substring("query", 2)

uery

substring-before("query", "er")

qu

substring-before("queryquery", "er")

qu

substring-after("query", "er")

y

substring-after("queryquery", "er")

yquery

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