CODEWITHSUNDEEP
sparqlrdf4j
vaishalir
vaishalir

Reputation: 65

How to use the MONTH() function from SPARQL to extract the month of a date in rdf4j?

How do I replicate the following filter from SPARQL in java using rd4j?

FILTER(?endDate > NOW() && ?startDate < NOW() && MONTH(?endDate) = MONTH(NOW()))

I have initialised expressions for MONTH() and NOW() as follows, and a graph pattern pattern, but don't know how to use them to extract the month from variable ?endDate and from the NOW() function

    Expression<?> nowFunc = Expressions.function(SparqlFunction.NOW );
    Expression<?> month = Expressions.function(SparqlFunction.MONTH);
    
    Expression<?> endDateGreaterThan = Expressions.gt(endDate, nowFunc);
    Expression<?> startDateLessThan = Expressions.lt(startDate, nowFunc);

The query I have so far is as follows, but I can't figure out how to implement the final part (****) of the filter into the query.

SelectQuery query = Queries.SELECT().prefix(ex).select(letter).where(pattern.filter(Expressions.
and(endDateGreaterThan, startDateLessThan, ****)

Upvotes: 1

Views: 273

Answers (1)

Jeen Broekstra
Jeen Broekstra

Reputation: 22053

It's no different from how you have set up your other expressions. You want an equals comparison operation between two value expressions (let's call them leftArg and rightArg), so:

Expression monthEquals = Expressions.equals(leftArg, rightArg);

Your leftArg and rightArg are both also functions, both with a single operand. The leftArg has a simple variable as its function operand:

Expression leftArg = Expressions.function(SparqlFunction.MONTH, endDate);

The rightArg has a NOW() function as its operand:

Expression rightArg = Expressions.function(SparqlFunction.MONTH,
        Expressions.function(SparqlFunction.NOW));

Just put it all together and you're done.

Upvotes: 0

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