[ORACLE]DÉTERMINER LA DATE DU PREMIER JOUR D'UNE SEMAINE PAR LE NUMÉRO DE SEMAINE

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-- Retrieve first date of week 
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FUNCTION getFirstDateOfWeek(vi_week_number IN  INTEGER,
		 					vi_year		   IN  INTEGER)
                            RETURN DATE
IS
v_first_monday_of_the_year INTEGER;
v_value INTEGER;

BEGIN

v_first_monday_of_the_year := -1;
v_value := 0;

	WHILE v_value <> 2 /*Find first Monday*/
	LOOP
	  	  v_first_monday_of_the_year := v_first_monday_of_the_year + 1; 
		  v_value := TO_CHAR(TO_DATE(vi_year || '0101', 'YYYYMMDD') + v_first_monday_of_the_year, 'D');	
	END LOOP;	  
	
	RETURN TO_DATE(vi_year || '0101', 'YYYYMMDD')+(v_first_monday_of_the_year + (7 * (vi_week_number - 2)));
	
END;