MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table table1 (ID int, Acreage decimal(10,2), Fvalue decimal(8, 4), Type int);
insert into table1 values
(1,16.24,null,1),
(2,2.17,null,1),
(3,138.00,null,3),
(4,138.00,null,1),
(5,142.47,null,3),
(6,6.16,null,2),
(7,14.80,null,2),
(8,26.01,null,1),
(9,26.01,null,3),
(10,1.45,null,3)
;

create table table2 (Acreage int, Factor decimal(8, 4), Type int);
insert into table2 values
(0,3.35,1),
(1,3.35,1),
(3,2.3,1),
(5,1.92,1),
(10,1.42,1),
(15,1.2,1),
(20,1,1),
(999,1,1),
(0,2.22,2),
(1,2.22,2),
(3,1.97,2),
(5,1.76,2),
(10,1.55,2),
(15,1.32,2),
(20,1.07,2),
(22,1,2),
(999,1,2),
(0,6.93,3),
(1,6.93,3),
(3,5.39,3),
(5,4.05,3),
(10,2.51,3),
(15,2.08,3),
(20,1.69,3),
(25,1.31,3),
(30,1,3),
(999,1,3);


SET @a := null;
SET @d := null;
SET @bin := null;
set @e := null;

UPDATE table1 temp,
(	SELECT 
		Acreage, 
		IF(
			base_col IS NULL, 
			(old_Factor +((Acreage - old_Acreage)/(new_Acreage - old_Acreage) ) * (new_Factor - old_Factor)), 
			base_col
		) AS update_col
	FROM
	(	SELECT *, 
		IF(Factor IS NULL, test, Factor) AS new_Factor,
		IF(Factor IS NULL, @BIN, @BIN := Factor) AS old_Factor,
		IF(test1 IS NULL, @D, @D := test1) AS new_Acreage,
		IF(test1 IS NULL, @E, @E := Acreage) AS old_Acreage,
		@A := Factor AS base_col
		FROM
		(    SELECT t1.Acreage, t2.Factor,
				(SELECT Factor FROM table2 WHERE Acreage > t1.Acreage ORDER BY Acreage LIMIT 1) test,
				(SELECT Acreage FROM table2 WHERE Acreage > t2.Acreage ORDER BY Acreage LIMIT 1) test1
			FROM table1 t1
			LEFT JOIN table2 t2 ON t2.Type = t1.Type
		)t4
	ORDER BY Acreage
	) tt
)temp1
SET temp.Fvalue = (ceiling(temp1.update_col * 1000) / 1000)
	WHERE temp.Acreage = temp1.Acreage;

Records: 10  Duplicates: 0  Warnings: 0



Records: 27  Duplicates: 0  Warnings: 0



Rows matched: 10  Changed: 10  Warnings: 4


select * from table2;


Acreage
Factor
Type


0
3.3500
1

1
3.3500
1

3
2.3000
1

5
1.9200
1

10
1.4200
1

15
1.2000
1

20
1.0000
1

999
1.0000
1

0
2.2200
2

1
2.2200
2

3
1.9700
2

5
1.7600
2

10
1.5500
2

15
1.3200
2

20
1.0700
2

22
1.0000
2

999
1.0000
2

0
6.9300
3

1
6.9300
3

3
5.3900
3

5
4.0500
3

10
2.5100
3

15
2.0800
3

20
1.6900
3

25
1.3100
3

30
1.0000
3

999
1.0000
3


select 
  a.id,
  a.acreage,
  case when lo.type is not null and hi.type is not null
       then lo.factor + (a.acreage - lo.acreage)
                      / (hi.acreage - lo.acreage)
                      * (hi.factor - lo.factor)
  end as fvalue,
  a.type
from table1 a,
lateral (
  select *
  from table2 b
  where b.type = a.type and b.acreage <= a.acreage
  order by b.acreage desc
  limit 1
) lo,
lateral (
  select *
  from table2 b
  where b.type = a.type and b.acreage > a.acreage
  order by b.acreage
  limit 1
) hi


id
acreage
fvalue
type


1
16.24
1.1504000000
1

2
2.17
2.7357500000
1

3
138.00
1.0000000000
3

4
138.00
1.0000000000
1

5
142.47
1.0000000000
3

6
6.16
1.7112800000
2

7
14.80
1.3292000000
2

8
26.01
1.0000000000
1

9
26.01
1.2473800000
3

10
1.45
6.5835000000
3

Acreage	Factor	Type
0	3.3500	1
1	3.3500	1
3	2.3000	1
5	1.9200	1
10	1.4200	1
15	1.2000	1
20	1.0000	1
999	1.0000	1
0	2.2200	2
1	2.2200	2
3	1.9700	2
5	1.7600	2
10	1.5500	2
15	1.3200	2
20	1.0700	2
22	1.0000	2
999	1.0000	2
0	6.9300	3
1	6.9300	3
3	5.3900	3
5	4.0500	3
10	2.5100	3
15	2.0800	3
20	1.6900	3
25	1.3100	3
30	1.0000	3
999	1.0000	3

id	acreage	fvalue	type
1	16.24	1.1504000000	1
2	2.17	2.7357500000	1
3	138.00	1.0000000000	3
4	138.00	1.0000000000	1
5	142.47	1.0000000000	3
6	6.16	1.7112800000	2
7	14.80	1.3292000000	2
8	26.01	1.0000000000	1
9	26.01	1.2473800000	3
10	1.45	6.5835000000	3