How to generalize or parameterize the SQL query - sql

Question

I have a problem with my employee_det table, where I am categorizing year wise active employee status.
for example1: an employee joined in 01-01-2017 and released from company in 02-02-2018 then he/she fall under 2017 bucket.
example2: If an employee joined in 01-02-2018 and released in 01-15-2019 then he will be under 2018 bucket.
if an employee joined in 01-01-2017 and he is still continuing in company then he must fall under 2019.
I have written the following query and which is giving me accurate results, but next year I need to add one more entry in WHERE condition, instead of that is there is any generalized way to solve this.
select emp_id, ename, year(effective_start_date) as year_bucket
from employee_det
where worker_status = 'Active'
and manager_name like '%srinivas%'
and (
( date(effective_start_date) <= '2017-12-31'
and date(effective_end_date)>='2017-12-31' )
or
( date(effective_start_date) <= '2018-12-31'
and date(effective_end_date)>='2018-12-31' )
or
( date(effective_start_date) <= current_date()
and date(effective_end_date)>=current_date()
)

Answer 1

You seem to want the start year for employees who have ended and the current year for active employees. So:
select emp_id, ename,
(case when effective_end_date > current_date
then year(current_date)
else year(effective_start_date)
end) as year_bucket
from employee_det
where worker_status = 'Active' and
manager_name like '%srinivas%';

Answer 2

Below is for BigQuery Standard SQL
#standardSQL
SELECT emp_id, ename,
EXTRACT(YEAR FROM IF(effective_end_date >= CURRENT_DATE, CURRENT_DATE, effective_start_date)) year_bucket
FROM `project.dataset.employee_det`
WHERE worker_status = 'Active'
AND manager_name LIKE '%srinivas%'
You can test, play with above using dummy data as in example below
#standardSQL
WITH `project.dataset.employee_det` AS (
SELECT 1 emp_id, 'employee1' ename, DATE '2017-01-01' effective_start_date, DATE '2018-02-02' effective_end_date, 'Active' worker_status, 'srinivas' manager_name UNION ALL
SELECT 2, 'employee2', '2018-01-02', '2019-01-15', 'Active', 'srinivas' UNION ALL
SELECT 3, 'employee3', '2017-01-01', '2019-04-15', 'Active', 'srinivas'
)
SELECT emp_id, ename,
EXTRACT(YEAR FROM IF(effective_end_date >= CURRENT_DATE, CURRENT_DATE, effective_start_date)) year_bucket
FROM `project.dataset.employee_det`
WHERE worker_status = 'Active'
AND manager_name LIKE '%srinivas%'
with result
Row emp_id ename year_bucket
1 1 employee1 2017
2 2 employee2 2018
3 3 employee3 2019
Update - excluding employees whose start and end YEAR is the same
You can just use one "generic" clause as below
WHERE EXTRACT(YEAR FROM effective_start_date) != EXTRACT(YEAR FROM effective_end_date)
so, the whole query now will be as in below example
#standardSQL
WITH `project.dataset.employee_det` AS (
SELECT 1 emp_id, 'employee1' ename, DATE '2017-01-01' effective_start_date, DATE '2018-02-02' effective_end_date, 'Active' worker_status, 'srinivas' manager_name UNION ALL
SELECT 2, 'employee2', '2018-01-02', '2019-01-15', 'Active', 'srinivas' UNION ALL
SELECT 3, 'employee3', '2017-01-01', '2019-04-15', 'Active', 'srinivas' UNION ALL
SELECT 4, 'employee4', '2017-01-01', '2017-04-15', 'Active', 'srinivas'
)
SELECT emp_id, ename,
EXTRACT(YEAR FROM IF(effective_end_date >= CURRENT_DATE, CURRENT_DATE, effective_start_date)) year_bucket
FROM `project.dataset.employee_det`
WHERE worker_status = 'Active'
AND manager_name LIKE '%srinivas%'
AND EXTRACT(YEAR FROM effective_start_date) != EXTRACT(YEAR FROM effective_end_date)
with result
Row emp_id ename year_bucket
1 1 employee1 2017
2 2 employee2 2018
3 3 employee3 2019
as you can see - employee4 is not included in any bucket