SQL Query Tuning with UNIONs

Question

HI:
Can some please give some hints for the better performane of the following query:
Select a.Hedged_Trade_ID, min(a.Trade_Date) Trade_Date, a.DealStartDate, a.MaturityDate
FROM
( Select      distinct a.Hedged_Trade_ID,
               a.Trade_Date,
               b.Trade_Date DealStartDate,
               b.Maturity_Date MaturityDate
From          CMS_FUTURES_TRANS a, CMS_PAS_ACCT_TRADE b
Where     trunc(a.LAST_UPDATE) = to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.Trade_Date < to_date(paramRunDate, 'mm/dd/yyyy')
AND           b.org_trade_id = to_number(decode(substr(a.Hedged_Trade_Id,1,1), 'U', 0, a.Hedged_Trade_Id))
AND           b.fgic_company = paramCompany
UNION
Select     distinct a.Hedged_Trade_ID,
               a.Trade_Date,
               b.Trade_Date DealStartDate,
               b.Maturity_Date MaturityDate
From          CMS_SWAP_ALLOC a, CMS_PAS_ACCT_TRADE b
Where           trunc(a.LAST_UPDATE) = to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.Trade_Date < to_date(paramRunDate, 'mm/dd/yyyy')
AND           b.org_trade_id = to_number(decode(substr(a.Hedged_Trade_Id,1,1), 'U', 0, a.Hedged_Trade_Id))
AND           b.fgic_company = paramCompany
UNION
Select      distinct a.Hedged_Trade_ID,
               a.Trade_Date,
               to_date('01/01/2001', 'mm/dd/yyyy') DealStartDate,
               to_date('01/01/9999', 'mm/dd/yyyy') MaturityDate
From           CMS_FUTURES_TRANS a
Where      trunc(a.LAST_UPDATE) = to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.Trade_Date < to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.hedged_trade_id IN (     Select     unassigned_id
          From     cms_fas_company
          Where      company_id = paramCompany)
UNION
Select      distinct a.Hedged_Trade_ID,
               a.Trade_Date,
               to_date('01/01/2001', 'mm/dd/yyyy') DealStartDate,
               to_date('01/01/9999', 'mm/dd/yyyy') MaturityDate
From          CMS_SWAP_ALLOC a
Where           trunc(a.LAST_UPDATE) = to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.Trade_Date < to_date(paramRunDate, 'mm/dd/yyyy')
AND           a.hedged_trade_id IN (     Select      unassigned_id
     From      cms_fas_company
     Where      company_id = paramCompany)
UNION
Select      distinct to_char(a.Org_Trade_id) Hedged_Trade_ID,
               a.History_Date Trade_Date,
               b.Trade_Date DealStartDate,
               b.Maturity_Date MaturityDate
From           CMS_PAS_ACCT_TRADE_HIST a, CMS_PAS_ACCT_TRADE b
Where           trunc(a.LAST_UPDATE) = to_date(paramRunDate + 1, 'mm/dd/yyyy')
AND           a.History_Date < to_date(paramRunDate, 'mm/dd/yyyy')
AND           b.org_trade_id = a.org_trade_id
AND           b.fgic_company = paramCompany
UNION
Select          distinct c.Hedged_Trade_id,
               DECODE(ABS(to_date(a.History_Date,'mm/dd/yyyy') - to_date(c.Trade_Date,'mm/dd/yyyy')),                     to_date(a.History_Date,'mm/dd/yyyy') - to_date(c.Trade_Date,'mm/dd/yyyy'),                     to_date(a.History_Date,'mm/dd/yyyy'), to_date(c.Trade_Date,'mm/dd/yyyy')) Trade_Date,
               b.Trade_Date DealStartDate,
               b.Maturity_Date MaturityDate
From           CMS_PAS_ACCT_TRADE_HIST a, CMS_PAS_ACCT_TRADE b, CMS_SWAP_ALLOC c
Where           c.swap_trade_id = a.org_trade_id
AND           b.org_trade_id = to_number(decode(substr(c.hedged_trade_id,1,1), 'U', 0, c.hedged_trade_id))
AND           b.fgic_company = paramCompany
AND           trunc(a.LAST_UPDATE) = to_date(paramRunDate + 1, 'mm/dd/yyyy')
AND           trunc(a.History_Date) < to_date(paramRunDate, 'mm/dd/yyyy')
AND           c.trade_date =      (     Select     MAX(trade_date)
          from     CMS_SWAP_ALLOC d
          Where     d.swap_trade_id = c.swap_trade_id
          AND     d.trade_date <= to_date(paramRunDate, 'mm/dd/yyyy')) ) a
Group By a.Hedged_Trade_ID, a.DealStartDate, a.MaturityDate;

Answer 1

Overall I suggest taking each one of your selects and running an explain plan to confirm they are behaving well in your database.
How many rows does this select return? Big IN lists can be bad
    a.hedged_trade_id in(select unassigned_id
                                    from   cms_fas_company
                                    where  company_id = paramcompany)This can be rewritten
   and exists (select 1
                    from   cms_fas_company
                    where  company_id = paramcompany
                    and unassigned_id  =  a.hedged_trade_id in
)