oracle calculate the average of the current and previous row values - oracle

Question

I have the following table which contains a single column VALUE1, I would like to calculate the average between the previous row and current row in VALUE1 and represent it in a second column VALUE2 starting from the second row i.e. The first row value will not be averaged.
The result should look like
ID VALUE1 VALUE2
1 3 3
2 4 3.5
3 5 4.5
4 5 5
5 6 5.5
6 2 4
NOTE: For first row (ID = 1) I average the first row with it self.
Any help appreciated. Thanks in advance.

Answer 1

You can also use the AVG() analytic function with a window of the previous and current row:
WITH practicenew AS (SELECT 1 ID, 3 value1 FROM dual UNION ALL
SELECT 2 ID, 4 value1 FROM dual UNION ALL
SELECT 3 ID, 5 value1 FROM dual UNION ALL
SELECT 4 ID, 5 value1 FROM dual UNION ALL
SELECT 5 ID, 6 value1 FROM dual UNION ALL
SELECT 6 ID, 2 value1 FROM dual)
SELECT ID,
value1,
AVG(value1) OVER (ORDER BY ID
ROWS BETWEEN 1 PRECEDING AND CURRENT ROW) value2
FROM practicenew;
ID VALUE1 VALUE2
---------- ---------- ----------
1 3 3
2 4 3.5
3 5 4.5
4 5 5
5 6 5.5
6 2 4

Answer 2

I think you can use this query, it gives the same output you have mentioned.
Create table script:
create table practicenew (ID number, Value1 number) ;
insert into practicenew (ID, Value1) values (1, 3) ;
insert into practicenew (ID, Value1) values (2,4) ;
insert into practicenew (ID, Value1) values (3,5);
insert into practicenew (ID, Value1) values (4,5);
insert into practicenew (ID, Value1) values (5,6);
insert into practicenew (ID, Value1) values (6,2 );
Then use NVL and Lag function. Lag will bring your previous value to current row and nvl is being used for the first row, as you will have null value in the first row while using lag.
Query: select ID, value1,nvl(((lag(value1) over (order by ID) + value1)/2),value1) as Value2
from practicenew;
Output:
ID Value1 Value2
1 3 3
2 4 3.5
3 5 4.5
4 5 5
5 6 5.5
6 2 4
I hope it helps!