Some question about FBI and Index on unique column

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Anyone can explain for me this issues.



1/ Which function-based-index(FBI) should I create and not ?



I heared from stranger who active in this forum that we should avoid create FBI as RTRIM, TO_CHAR, UPPER, TRUNC, others are ok. Is it true? And why?



2/ For ex: I have an Index like "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB"



In that, STUDENTS is table, STUDENTID is PK, CLASSID is Unique.



And I have a procedure that contain the statement: SELECT CLASSID, NAME FROM STUDENTS WHERE CLASSID = '8A'.



Of course it will use the index "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB".



And my question is: should I create an index like IX_STUDENTS_CLASSID. This might be a silly question to ask but sometimes, I saw the SQL Tuning Advisor recommended about create it.










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    0















    Anyone can explain for me this issues.



    1/ Which function-based-index(FBI) should I create and not ?



    I heared from stranger who active in this forum that we should avoid create FBI as RTRIM, TO_CHAR, UPPER, TRUNC, others are ok. Is it true? And why?



    2/ For ex: I have an Index like "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB"



    In that, STUDENTS is table, STUDENTID is PK, CLASSID is Unique.



    And I have a procedure that contain the statement: SELECT CLASSID, NAME FROM STUDENTS WHERE CLASSID = '8A'.



    Of course it will use the index "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB".



    And my question is: should I create an index like IX_STUDENTS_CLASSID. This might be a silly question to ask but sometimes, I saw the SQL Tuning Advisor recommended about create it.










    share|improve this question







    New contributor




    Windy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.























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      0








      Anyone can explain for me this issues.



      1/ Which function-based-index(FBI) should I create and not ?



      I heared from stranger who active in this forum that we should avoid create FBI as RTRIM, TO_CHAR, UPPER, TRUNC, others are ok. Is it true? And why?



      2/ For ex: I have an Index like "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB"



      In that, STUDENTS is table, STUDENTID is PK, CLASSID is Unique.



      And I have a procedure that contain the statement: SELECT CLASSID, NAME FROM STUDENTS WHERE CLASSID = '8A'.



      Of course it will use the index "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB".



      And my question is: should I create an index like IX_STUDENTS_CLASSID. This might be a silly question to ask but sometimes, I saw the SQL Tuning Advisor recommended about create it.










      share|improve this question







      New contributor




      Windy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.












      Anyone can explain for me this issues.



      1/ Which function-based-index(FBI) should I create and not ?



      I heared from stranger who active in this forum that we should avoid create FBI as RTRIM, TO_CHAR, UPPER, TRUNC, others are ok. Is it true? And why?



      2/ For ex: I have an Index like "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB"



      In that, STUDENTS is table, STUDENTID is PK, CLASSID is Unique.



      And I have a procedure that contain the statement: SELECT CLASSID, NAME FROM STUDENTS WHERE CLASSID = '8A'.



      Of course it will use the index "IX_STUDENTS_STUDENTID_CLASSID_NAME_DOB".



      And my question is: should I create an index like IX_STUDENTS_CLASSID. This might be a silly question to ask but sometimes, I saw the SQL Tuning Advisor recommended about create it.







      oracle-12c index-tuning






      share|improve this question







      New contributor




      Windy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question







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      Windy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









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      share|improve this question






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      asked 13 mins ago









      WindyWindy

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      Check out our Code of Conduct.






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