create table t1 (
pk int primary key,
a int,
b int,
c real
);
insert into t1 values
(101 , 0, 10, 1.1),
(102 , 0, 10, 2.1),
(103 , 1, 10, 3.1),
(104 , 1, 10, 4.1),
(108 , 2, 10, 5.1),
(105 , 2, 20, 6.1),
(106 , 2, 20, 7.1),
(107 , 2, 20, 8.15),
(109 , 4, 20, 9.15),
(110 , 4, 20, 10.15),
(111 , 5, NULL, 11.15),
(112 , 5, 1, 12.25),
(113 , 5, NULL, 13.35),
(114 , 5, NULL, 14.50),
(115 , 5, NULL, 15.65),
(116 , 6, 1, NULL),
(117 , 6, 1, 10),
(118 , 6, 1, 1.1),
(119 , 6, 1, NULL),
(120 , 6, 1, NULL),
(121 , 6, 1, NULL),
(122 , 6, 1, 2.2),
(123 , 6, 1, 20.1),
(124 , 6, 1, -10.4),
(125 , 6, 1, NULL),
(126 , 6, 1, NULL),
(127 , 6, 1, NULL);
select pk, a, b, avg(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
from t1;
pk	a	b	avg(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
101	0	10	10.0000
102	0	10	10.0000
103	1	10	10.0000
104	1	10	10.0000
105	2	20	20.0000
106	2	20	20.0000
107	2	20	16.6667
108	2	10	15.0000
109	4	20	20.0000
110	4	20	20.0000
111	5	NULL	1.0000
112	5	1	1.0000
113	5	NULL	1.0000
114	5	NULL	NULL
115	5	NULL	NULL
116	6	1	1.0000
117	6	1	1.0000
118	6	1	1.0000
119	6	1	1.0000
120	6	1	1.0000
121	6	1	1.0000
122	6	1	1.0000
123	6	1	1.0000
124	6	1	1.0000
125	6	1	1.0000
126	6	1	1.0000
127	6	1	1.0000
select pk, a, c, avg(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
from t1;
pk	a	c	avg(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
101	0	1.1	1.6
102	0	2.1	1.6
103	1	3.1	3.5999999999999996
104	1	4.1	3.5999999999999996
105	2	6.1	6.6
106	2	7.1	7.116666666666667
107	2	8.15	6.783333333333334
108	2	5.1	6.625000000000001
109	4	9.15	9.65
110	4	10.15	9.65
111	5	11.15	11.7
112	5	12.25	12.25
113	5	13.35	13.366666666666667
114	5	14.5	14.5
115	5	15.65	15.075
116	6	NULL	10
117	6	10	5.55
118	6	1.1	5.55
119	6	NULL	1.0999999999999996
120	6	NULL	NULL
121	6	NULL	2.1999999999999997
122	6	2.2	11.15
123	6	20.1	3.966666666666667
124	6	-10.4	4.85
125	6	NULL	-10.400000000000002
126	6	NULL	NULL
127	6	NULL	NULL
drop table t1;