SPARQL how to make DAY/MONTH always return 2 digits-CodePudding

I have a datetime in my SPARQL-query that I want to transform to a date. Therefore I do:

 BIND(CONCAT(YEAR(?dateTime), "-",MONTH(?dateTime), "-", DAY(?dateTime)) as ?date)

This part of code works but returns for example 2022-2-3, I want it to be 2022-02-03. If the dateTime is 2022-11-23, nothing should change.

CodePudding user response：

You can take the integers you get back from the YEAR, MONTH, and DAY functions and pad them with the appropriate number of zeros (after turning them into strings):

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT * WHERE {
    BIND(2022 AS ?yearInt) # this would come from your YEAR(?dateTime) call
    BIND(2 AS ?monthInt)   # this would come from your MONTH(?dateTime) call
    BIND(13 AS ?dayInt)    # this would come from your DAY(?dateTime) call

    # convert to strings
    BIND(STR(?yearInt) AS ?year)
    BIND(STR(?monthInt) AS ?month)
    BIND(STR(?dayInt) AS ?day)

    # pad with zeros
    BIND(CONCAT("00", ?year) AS ?paddedYear)
    BIND(CONCAT("0000", ?month) AS ?paddedMonth)
    BIND(CONCAT("00", ?day) AS ?paddedDay)

    # extract the right number of digits from the padded strings
    BIND(SUBSTR(?paddedYear, STRLEN(?paddedYear)-3) AS ?fourDigitYear)
    BIND(SUBSTR(?paddedDay, STRLEN(?paddedDay)-1) AS ?twoDigitDay)
    BIND(SUBSTR(?paddedMonth, STRLEN(?paddedMonth)-1) AS ?twoDigitMonth)
    
    # put it all back together
    BIND(CONCAT(?fourDigitYear, "-", ?twoDigitMonth, "-", ?twoDigitDay) as ?date)
}

CodePudding user response：

@gregory-williams gives a portable answer. An alternative is functions from F&O (XPath and XQuery Functions and Operators 3.1) "fn:format-...."

I'm not sure of the coverage in various triplestores - Apache Jena provides fn:format-number, which is needed for the question, but not fn-format-dateTime etc

See
https://www.w3.org/TR/xpath-functions-3/#formatting-the-number
https://www.w3.org/TR/xpath-functions-3/#formatting-dates-and-times

For example:

fn:format-number(1,"000") returns the string "001".

Apache Jena also has a local extension afn:sprintf using the C or Java syntax of sprintf:

afn:sprintf("d", 1) returns "001".