SQL Developer - Pulling column value from previous row

Question

I am using Oracle SQL developer and trying to pull a value from a column from the previous row.
Currently this is an example from the code im using.
Select CD1.nbr_dw, CD1.SEQ_DW, CD1.CDL_NET_PAID, CD1.UNITS_ALLOW,CD1.ALLOW_AMT, CD1.UNIT_PRICE, CD1.BACKED_OUT,
case
When CD1.NET_PAID = 0 then 0
****NEW CODE*****
Else CD1.ALLOW_AMT / CD1.UNIT_PRICE
end as NEW_UNITS
From Table_A CD1
join (Select nbr_dw, DET_DW, SEQ_DW
From Table_B
) CD2
on CD1.nbr_dw = CD2.nbr_dw
I need to add another when statement that says when CD1.BACKED_OUT = 'Y' populated the NEW_UNITS field with the previous rows value of CD1.UNIT_PRICE. Note, the CD1.SEQ_DW can be used to determine the previous row. Any ideas?

Answer 1

Hi,
Welcome to the forum!
The analytic LAG function can return a value from the previous row:
LAG (cd1.unit_price) OVER ( -- PARTITION BY  x          -- if needed
                               ORDER BY          cd1.seq_dw
                 )It's unclear if you need a PARTITION BY clause or not.
"PARTITION BY x" means that you want the value from the last row that has the same value of x as the current row.
If you omit the PARTITION BY clause, it means you want the last row regardless of what any other columns are.
Whenever you have a problem, it ehlps if you post a little sample data (CREATE TABLE and INSERT statements) and the results you want from that data.
Explain how you get those results from that data.
Always say what version of Oracle you're using.