Measuring Elapsed Time to Run a SQL Query in PL/SQL

DECLARE 
   t1   timestamp;
   t2   timestamp;
BEGIN
   t1 := systimestamp; 

   FOR i IN 1..1000 LOOP
      Dbms_Output.Put_Line(TO_CHAR(i));
   END LOOP;
   
   t2 := systimestamp; 

   Dbms_Output.Put_Line('Start: ' || t1); 
   Dbms_Output.Put_Line('  End: ' || t2); 
   Dbms_Output.Put_Line('Elapsed Seconds: ' || TO_CHAR(t2 - t1, 'SSSS.FF'));
END;

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