Previous Available date in a column

Question

I Have a colum date and a amount. If select a date i need to fetch the previous avaialble amount
In the below case
WITH table_1 AS
(select '700' amount,'01/01/2011' date1 from dual union all
select '800' amount ,'12/23/2010' date1 from dual union all
select '900' amount, '11/31/2011' date1 from dual
select * from table_1;
if my where clause for date = '12/23/2010' then the amount should be '0' as no previous day amount avaialble.
if my where clause for date = '01/01/2011' then the amount should be '800' as the avaialble previous date is '12/23/2010'
if my where clause for date = '11/31/2011' then the amount should be '700'' as the avaialble previous date is '01/01/2011'
Please help
Edited by: user10285699 on Jan 24, 2011 5:47 PM

Answer 1

Hi,
user10285699 wrote:
... WITH table_1 AS
select '1' day, '10' id1,'100' amount,'12/30/2010' date1,'null' amount_pre_day from dual union all
select '1' day,'20' id1 ,'200' amount , '12/20/2010' date1 ,'null' amount_pre_day from dual union all
select '1' day, '30' id1, '300' amount, '10/28/2011' date1,'null' amount_pre_day from dual
select * from table_1;
The second day i need to calculate the previous AVAILABLE day amount and update another column "amount_pre_day"
WITH table_1 AS
(select '2' day, '10' id1,'400' amount,'12/31/2010' date1, '100' amount_pre_day from dual union all
select '2' day, '20' id1 ,'500' amount ,'12/22/2010' date1,'200' amount_pre_day from dual union all
select '2' day, '30' id1, '600' amount, '10/31/2011' date1,'300' amount_pre_day from dual
select * from table_1;
The tihrd day i need to calculate the previous AVAILABLE day amount and update another column "amount_pre_day"
WITH table_1 AS
(select '3' day, '10' id1,'700' amount,'01/01/2011' date1, '400' amount_pre_day from dual union all
select '3' day, '20' id1 ,'800' amount ,'12/23/2010' date1,'500' amount_pre_day from dual union all
select '3' day, '30' id1, '900' amount, '11/31/2011' date1,'600' amount_pre_day from dual
select * from table_1;Thanks for posting the sample data.
Always post the results you want from the sample data, too, and say what version of Oracle you're using.
Are those 3 different sets of sample data? I'm very confused by what you want.
Why is everything a string, including the word 'null'? In particular, it's a really bad idea to store dates in VARCHAR2 columns; you should use a DATE column instead.
What date is '11/31/2011' supposed to be?
My best guess as to what you mean is:
"I have the following table:
{code}
WITH table_1 AS
select '1' day, '10' id1, '100' amount, DATE '2010-12-30' date1, null amount_pre_day from dual union all
select '1' day, '20' id1, '200' amount, DATE '2010-12-20' date1, null amount_pre_day from dual union all
select '1' day, '30' id1, '300' amount, DATE '2011-10-28' date1, null amount_pre_day from dual union all
select '2' day, '10' id1, '400' amount, DATE '2010-12-31' date1, '100' amount_pre_day from dual union all
select '2' day, '20' id1, '500' amount, DATE '2010-12-22' date1, '200' amount_pre_day from dual union all
select '2' day, '30' id1, '600' amount, DATE '2011-10-31' date1, '300' amount_pre_day from dual union all
select '3' day, '10' id1, '700' amount, DATE '2011-01-01' date1, '400' amount_pre_day from dual union all
select '3' day, '20' id1, '800' amount, DATE '2010-12-23' date1, '500' amount_pre_day from dual union all
select '3' day, '30' id1, '900' amount, DATE '2011-11-30' date1, '600' amount_pre_day from dual
{code}
But I don't actually want to supply the amount_pre_day column; I want to compute that from the amount column of the previous row (where date1 determines what that means) for the same id1."
If that's what you meant, here's one way to get it:
SELECT       t.*
,       LAG (amount) OVER ( PARTITION BY  id1
                              ORDER BY         date1     -- or maybe day
                   )               AS calc_pre_day
FROM       table_1   t
ORDER BY  id1
,            date1
;Output:
D ID AMO DATE1       AMO CAL
1 10 100 30-Dec-2010
2 10 400 31-Dec-2010 100 100
3 10 700 01-Jan-2011 400 400
1 20 200 20-Dec-2010
2 20 500 22-Dec-2010 200 200
3 20 800 23-Dec-2010 500 500
1 30 300 28-Oct-2011
2 30 600 31-Oct-2011 300 300
3 30 900 30-Nov-2011 600 600As you can see, the last column (calc_pre_day) is the same as amount_pre_day.