I have this query that has a '+level' with the date. I am not sure what it is but executing the query gives the list of dates in an ascending order. Here's how the query looks like:
select date '2018-01-01' + level -1 dt
from dual connect by level <= 1000
Any guidance?
CONNECT BY specifies the relationship between parent rows and child rows of the hierarchy.
More information here - Hierarchical Queries
So the date 01-JAN-18 would be at root (level 1) and then the dates forward (restricted to 1000 levels) would be children.
Level 1 would be a parent for Level 2 and so on.
select date '2018-01-01' + level -1 dt, LEVEL
from dual connect by level <= 1000
For more, refer to this example from here.
SELECT employee_id, last_name, manager_id FROM employees CONNECT BY PRIOR employee_id = manager_id;
EMPLOYEE_ID LAST_NAME MANAGER_ID
101 Kochhar 100
108 Greenberg 101
109 Faviet 108
110 Chen 108
111 Sciarra 108
112 Urman 108
113 Popp 108
200 Whalen 101
Note here, the manager with id 100 is at the top of the organization.
While Shreyas is correct, a more simplified answer for your example is that "level" is like a variable that comes along when you use connect by and is like a counter for the connect by "loop". It will cause the query to be run 1000 times and level will hold the index as it loops. Here it's used in the calculation and will increment from 1 to 1000.
