level clause is responsible for generating N number of dummy records based on some specific condition.
SELECT ROWNUM NO FROM DUAL CONNECT BY LEVEL <= 10
/* This is a simple query which can generate a sequence of numbers. The following example generates a sequence of numbers from 1..100 */
select level from dual connect by level <= 100;
/*The above query is useful in various scenarios like generating a sequence of dates from a given date. The following query generates 10 consecutive dates */
select to_date('01-01-2017','mm-dd-yyyy')+level-1 as dates from dual connect by level <= 10;