SQL Pulling results by year - sql

Question

Problem: I have dated salary information stored in a table. I need to display one result per year. For each year, I want to display the max dated record from the year prior. The problem is that some years don’t have data (salary didn’t change). I need these rows to contain the max record prior to that year (it may be from 2 years before or even 3).
My query right now would work if each row has data… but it doesn’t account for years where there is no data. How can I update this sql to pull the desired results below:
Example of data:
sch_sal_svc.beg_date -------sch_sal_svc.beg_date.per_plan_data
1/1/2007---100
6/1/2007---200
1/1/2008---300
1/1/2011---400
8/1/2011---500
9/1/2012---600
Current Results
1/1/2008---200
1/1/2011---300
1/1/2012---500
Desired Results
1/1/2008---200
1/1/2009---300
1/1/2010---300
1/1/2011---300
1/1/2012---500
SQL:
SELECT
years.control_id,
years.ssn,
ebe.plan_id,
to_number(to_char(years.sal_date,'yyyy')),
null as per_plan_salary,
null as per_vest_hours,
null as per_credsvc_hours,
LEAST(s.rate_1,cl.comp_genl),
null as salary_1,
null as per_comm,
null as per_overtime,
null as per_ncr,
null as salary_2
FROM
sch_sal_svc s
, (select distinct ssn, control_id, TRUNC(beg_date,'YEAR') as sal_date from sch_sal_svc where beg_date > to_date('12/31/1900', 'mm/dd/yyyy')) years
, employee_benefit_elig ebe, compliance_limits cl
WHERE
years.ssn = ebe.ssn
and years.control_id = ebe.control_id
and to_number(to_char(years.sal_date,'yyyy')) = cl.limit_year
and to_number(to_char(years.sal_date,'yyyy')) <= to_number(to_char(sysdate,'yyyy'))
and s.beg_date = (
select max(s2.beg_date) from sch_sal_svc s2
where s2.ssn = years.ssn and s2.control_id = years.control_id
and s2.beg_date <= years.sal_date
)
and s.ssn = years.ssn
and s.control_id = years.control_id
and ebe.benefit_id = 'DB'
and ebe.control_id = 'CLIENT'
and ebe.plan_id in ('100', '200')

Answer 1

CREATE TABLE sch_sal_svc
(
beg_date DATE
, per_plan_data NUMBER
);
INSERT INTO sch_sal_svc VALUES(TO_DATE('01/01/2007', 'DD/MM/YYYY'), 100);
INSERT INTO sch_sal_svc VALUES(TO_DATE('06/01/2007', 'DD/MM/YYYY'), 200);
INSERT INTO sch_sal_svc VALUES(TO_DATE('01/01/2008', 'DD/MM/YYYY'), 300);
INSERT INTO sch_sal_svc VALUES(TO_DATE('01/01/2011', 'DD/MM/YYYY'), 400);
INSERT INTO sch_sal_svc VALUES(TO_DATE('08/01/2011', 'DD/MM/YYYY'), 500);
INSERT INTO sch_sal_svc VALUES(TO_DATE('09/01/2012', 'DD/MM/YYYY'), 600);
SELECT MIN(beg_date) FROM sch_sal_svc;
-- 2007-01-01 00:00:00
SELECT d.r_level + NUMTOYMINTERVAL(1, 'YEAR') AS d_date
, NVL -- the salary must be updated at least once in three years
(
NVL
(
NVL
(
s.per_plan_data
, LAG(s.per_plan_data, 1) OVER (PARTITION BY 1 ORDER BY d.r_level)
)
, LAG(s.per_plan_data, 2) OVER (PARTITION BY 1 ORDER BY d.r_level)
)
, LAG(s.per_plan_data, 3) OVER (PARTITION BY 1 ORDER BY d.r_level)
) AS lag_per_plan_data
FROM
(
SELECT DATE'2006-01-01' + NUMTOYMINTERVAL(LEVEL, 'YEAR') AS r_level -- min beg_date minus 1
FROM DUAL
CONNECT BY
LEVEL < (SELECT TO_CHAR(MAX(beg_date), 'YYYY') - TO_CHAR(MIN(beg_date), 'YYYY') + 2 FROM sch_sal_svc)
) d
LEFT JOIN
(
SELECT beg_date
, per_plan_data
FROM sch_sal_svc
WHERE (beg_date) IN
(
SELECT MAX(beg_date)
FROM sch_sal_svc
GROUP BY
TRUNC(beg_date, 'YYYY')
)
) s
ON d.r_level = TRUNC(s.beg_date, 'YYYY')
;
/*
2008-01-01 00:00:00 200
2009-01-01 00:00:00 300
2010-01-01 00:00:00 300
2011-01-01 00:00:00 300
2012-01-01 00:00:00 500
2013-01-01 00:00:00 600
*/