Sub-query got stuck !!!

Question

Data
fcst_retail_value (current Table)
fcst_entity_id period_id fcst LYfcst
100     2000     30     null
100     2002     40     null
100     2003     70     null
100 2001 50 null
200     3000     140 null
200     3001 400 null
300     8000     160 null
300     9000     260 null
300     4000     270 null
400     5000     440     null
400     6000     960     null
400 7000     900 null
retail_fcst_map
fcst_entity_id retail_entity_id
100               101
100               102
100               103
200               201
200               202
300               301
300               302
400               401
400               402
retail_bucket
retail_entity_id retail_type_cd retail Period_id
101          forecasted     30          2000
102          forecasted 40          2002
101     forecasted     50          2001
102 forecasted 70          2003
202 forecasted     140          3000
201 forecasted     150          3001
204 forecasted     250          3001
301 forecasted     160          8000
303 forecasted     260          9000
302 forecasted     270 4000
401 forecasted     330 6000
402 forecasted     440 5000
403 forecasted 500 7000
404 forecasted 400 7000
405 forecasted     630 6000
cal_period
period_id year cal_id
2001     2004 45
2000     2006 45
2002     2005 45
2003     2003 45
3000 2006 44
3001 2005 44
3002 2004 44
8000 2006 43
9000 2005 43
4000 2004 43
5000 2006 42
6000 2005 42
7000 2004 42
OUTPUT NEEDED
updating fcst_retail_value.lyrdmd with last years data not changing any other data within the table
fcst_retail_value (2006 DATA + LYDMD populated)
fcst_entity_id period_id fcst LYfcst
100          2000          30     40
100          2002          40     50
100          2003          70     null
100 2001 50 70
200          3000          140 400
200          3001 400 null
300          8000          160 260
300          9000          260 270
300          4000          270 null
400          5000          440     960
400          6000          960     900
400          7000          900 null
Tried this but I think i need to write a sub query to go further:
select sum(db_self.retail_value) as db,
cp.year, db_self.period_id as dbp,
cp.period_id as cpp,
fdv_parent.period_id as fdvp,
fdv_parent.fcst_entity_id as feid,
cp.cal_period_id as ccpid,
cp.cal_id as calid
cp_ly.year
from retail_fcst_map dfm, retail_bucket db_self, fcst_retail_value fdv_parent, cal_period cp,cal_period cp_ly
WHERE dfm.fcst_entity_id = 100
AND dfm.retail_entity_id = db_self.retail_entity_id
and db_self.period_id = fdv_parent.period_id
and dfm.fcst_entity_id = fdv_parent.fcst_entity_id
and fdv_parent.period_id = cp.period_id
AND cp_ly.year = cp.year - 1
Group By db_self.period_id, cp.year, db_self.period_id, cp.period_id, fdv_parent.period_id, fdv_parent.fcst_entity_id, cp.cal_period_id, cp.cal_id;
Thanks
mohan

Answer 1

OUTPUT NEEDED
I need to update fcst_retail_value.lyfcst with last years data not changing any other data within the table
fcst_retail_value (2006 DATA + LYDMD populated)
fcst_entity_id period_id fcst LYfcst
100 2000 30 40
100 2002 40 50
100 2003 70 null
100 2001 50 70
200 3000 140 400
200 3001 400 null
300 8000 160 260
300 9000 260 270
300 4000 270 null
400 5000 440 960
400 6000 960 900
400 7000 900 null