Postgres 13

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create table t1 (i_t1 int, tk varchar(5));
    
insert into t1 (i_t1, tk)
values (400,'t1'),(702,'t2');

select * from t1;

create table t2 (tk varchar(5), i1_t2 int, i2_t2 int, v real);

insert into t2 (tk, i1_t2, i2_t2, v)
values ('t20',300,600,0.5),('t19',350,550,0.6),('t18',370,420,0.7),('t17',500,800,0.2),('t16',623,751,0.9);

select * from t2;
2 rows affected



i_t1
tk


400
t1

702
t2


5 rows affected



tk
i1_t2
i2_t2
v


t20
300
600
0.5

t19
350
550
0.6

t18
370
420
0.7

t17
500
800
0.2

t16
623
751
0.9


SELECT
    *
FROM t1
JOIN t2 ON (t1.i_t1 BETWEEN t2.i1_t2 AND i2_t2)


i_t1
tk
tk
i1_t2
i2_t2
v


400
t1
t20
300
600
0.5

400
t1
t19
350
550
0.6

400
t1
t18
370
420
0.7

702
t2
t17
500
800
0.2

702
t2
t16
623
751
0.9


SELECT 
    t1.i_t1, t1.tk,
    SUM(t2.v)
FROM t1
JOIN t2 ON (t1.i_t1 BETWEEN t2.i1_t2 AND i2_t2)
GROUP BY t1.i_t1, t1.tk


i_t1
tk
sum


400
t1
1.8

702
t2
1.1

tk	i1_t2	i2_t2	v
t20	300	600	0.5
t19	350	550	0.6
t18	370	420	0.7
t17	500	800	0.2
t16	623	751	0.9

i_t1	tk	tk	i1_t2	i2_t2	v
400	t1	t20	300	600	0.5
400	t1	t19	350	550	0.6
400	t1	t18	370	420	0.7
702	t2	t17	500	800	0.2
702	t2	t16	623	751	0.9

tk	i1_t2	i2_t2	v
t20	300	600	0.5
t19	350	550	0.6
t18	370	420	0.7
t17	500	800	0.2
t16	623	751	0.9

i_t1	tk	tk	i1_t2	i2_t2	v
400	t1	t20	300	600	0.5
400	t1	t19	350	550	0.6
400	t1	t18	370	420	0.7
702	t2	t17	500	800	0.2
702	t2	t16	623	751	0.9

tk	i1_t2	i2_t2	v
t20	300	600	0.5
t19	350	550	0.6
t18	370	420	0.7
t17	500	800	0.2
t16	623	751	0.9

i_t1	tk	tk	i1_t2	i2_t2	v
400	t1	t20	300	600	0.5
400	t1	t19	350	550	0.6
400	t1	t18	370	420	0.7
702	t2	t17	500	800	0.2
702	t2	t16	623	751	0.9