SQL Server 2019

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CREATE TABLE scale_table(
   empl_id   VARCHAR(7) NOT NULL 
  ,scale_id  VARCHAR(9) NOT NULL
  ,date_from VARCHAR(11) NOT NULL
  ,date_to   VARCHAR(11) NOT NULL
);
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('187','B3EL9','2014-03-01','2017-06-30');
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('187','B4EL6','2017-07-01','2019-10-31');
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('187','B5EL9','2019-11-01','2099-12-31');
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('214','M115','2006-10-01','2099-12-31');
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('618','B3L9','2014-01-01','2019-10-31');
INSERT INTO scale_table(empl_id,scale_id,date_from,date_to) VALUES ('618','B6L9','2019-11-01','2099-12-31');
6 rows affected

CREATE TABLE value_table(
   scale_id  VARCHAR(9) NOT NULL 
  ,amount    VARCHAR(9) NOT NULL
  ,date_from VARCHAR(11) NOT NULL
  ,date_to   VARCHAR(11) NOT NULL
);
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3EL9','78084.00','2013-01-01','2015-06-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3EL9','81432.00','2015-07-01','2099-12-31');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B4EL6','78348.00','2013-01-01','2015-06-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B4EL6','81720.00','2015-07-01','2099-12-31');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B5EL9','95964.00','2013-01-01','2015-06-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B5EL9','100092.00','2015-07-01','2099-12-31');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3L9','52728.00','2013-01-01','2015-08-15');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3L9','54996.00','2015-08-16','2017-11-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3L9','56100.00','2017-12-01','2020-11-15');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B3L9','56664.00','2020-11-16','2099-12-31');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B6L9','64140.00','2013-01-01','2015-08-15');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B6L9','66900.00','2015-08-16','2017-11-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B6L9','68244.00','2017-12-01','2020-11-15');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('B6L9','68928.00','2020-11-16','2099-12-31');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('M115','108528.00','2012-07-01','2015-06-30');
INSERT INTO value_table(scale_id,amount,date_from,date_to) VALUES ('M115','115128.00','2015-07-01','2099-12-31');
16 rows affected

select s.empl_id,
	s.scale_id,
	v.amount,
	case when s.date_from <= v.date_from then v.date_from else s.date_from end as date_from,
	case when v.date_to <= s.date_from then v.date_to else s.date_to end as date_to
from scale_table s
inner join value_table v 
	on  s.scale_id = v.scale_id
	and s.date_from <= v.date_to
	and s.date_to   >= v.date_from
where s.empl_id = 187


empl_id
scale_id
amount
date_from
date_to


187
B3EL9
78084.00
2014-03-01
2017-06-30

187
B3EL9
81432.00
2015-07-01
2017-06-30

187
B4EL6
81720.00
2017-07-01
2019-10-31

187
B5EL9
100092.00
2019-11-01
2099-12-31
empl_id	scale_id	amount	date_from	date_to
187	B3EL9	78084.00	2014-03-01	2017-06-30
187	B3EL9	81432.00	2015-07-01	2017-06-30
187	B4EL6	81720.00	2017-07-01	2019-10-31
187	B5EL9	100092.00	2019-11-01	2099-12-31