Hello, 
 
QUESTION1: Can somebody clarify in what of the proposed scenarios is the following index used? Any further comment will be greatly appreciated.
 
QUESTION2: Does any other scenarios when an index is NOT used (and someone might possibly expect it is used) come to your mind? Thank you very much for your time and wish you a happy dayJ
 
CREATE INDEX idx_margincall_bussdt ON margincall USING btree (businessdate);
 
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SCENARIO 1:
select MC.IDTRADINGACCOUNT
          from MARGINCALL MC
            join DEFAULTINGACCOUNT DA on DA.BUSINESSDATE = MC.BUSINESSDATE and DA.IDTRADINGACCOUNT = MC.IDTRADINGACCOUNT
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SCENARIO 2:
select MC.IDTRADINGACCOUNT
          from MARGINCALL MC
where MC.BUSINESSDATE = '17.11.2008';
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SCENARIO 3:
select MC.IDTRADINGACCOUNT
          from MARGINCALL MC
            join DEFAULTINGACCOUNT DA on DA.BUSINESSDATE = MC.BUSINESSDATE and DA.IDTRADINGACCOUNT = MC.IDTRADINGACCOUNT
where MC.BUSINESSDATE = '17.11.2008';
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SCENARIO 4 + QUESTION:
Is usage of indexes during execution of queries affected by db-links?
E.g.:
select MC.IDTRADINGACCOUNT
          from MARGINCALL@DB_LINK_NAME MC
where MC.BUSINESSDATE = '17.11.2008';
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Adam Slachta