Choice of index when 2 index have similar columns

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• Unique index on two columns based on the conditon

  I have a table where I have two columns name and feed.
  

  create table test1 (name varchar(20), feed varchar(4));
  
  insert into test1 values('abc','L3');
  insert into test1 values( 'abc','Both');
  insert into test1 values('abc','L2');

  I want to create a unique index for the lines abc - L3 and cant abc - both together be inserted, rest the other flow values is not a problem, so the first two rows can not be there in the table.
  
  Please suggest
  
  Thajs

  create unique index test1_ind1 on test1 (name, case when feed = 'Both' then 'L3' else feed end );
  

  Who did what you asked...

  However, I highly doubt it does what you WANT.

  Please provide information on the requirements, and we the flesh that out a little better.

• index on the column of low cardinality

  Hello
  Standard edition Oracle 10.2
  
  I have a 'status' column in my table. table contains about 100000 records.
  The possible values of status will be 1 or 2 (digital). This column will be 5 to 10 percent of the population, and the rest is null.
  
  Because it is seems that bitmap index is candidate for low cardinality column, but this picture has high of DML operations. SO by web research I learned about this bitmap causes problems of blocking on high DML operations.
  
  So I think that B-tree is only option left. Can you suggest a good index to improve performance on such a column?

  You don't need an index based on a function, do you think?

  You have a STATUS column where a small percentage of values is not null.

  To effectively access these lines whose STATUS is non-zero, simply create an index on the column State.

  This should be plenty effective.

  The effectiveness of this index (or the fbi if she was forced) is based on the fact that an index b-tree contains entry when the value is null (or all of the values in the case of a composite).

  There are those that 100000 is small and 5-10% is not particularly selective and you tell the width of the table, etc., so, even with the index here, it might not if used - i.e. depending on the circumstances it might be more efficient to do a FTS.

  It depends on what you want to do.

  See:
  http://asktom.Oracle.com/pls/asktom/f?p=100:11:0:P11_QUESTION_ID:4433887271030
  http://richardfoote.WordPress.com/2008/05/12/index-scan-or-full-table-scan-the-magic-number-magic-dance/

  Published by: Dom Brooks on February 10, 2011 12:58

• Index on two columns becomes the index of function?

  Hello, I create a unique index with two columns, a number (9) and a date.
  
  It becomes an index of feature based with the number column and a column sys hidden (date).
  
  When I do queries that use this index the autotrace tells me it does things like this:
  
  sys_nc00001$ > SYS_OP_DESCEND (datevalue)
  sys_nc00001$ IS NOT NULL
  
  How is he did not have a normal index?

  Use of ESCR does this.

  Of http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_5010.htm

  Oracle database processes Index descending as if they were focused on the index function.

• Best Index on a column with low cardinality on a high DML activity table?

  I wanted to ask a question about the indices? I have a table which is the main table in the my system it holds nearly 65 000-1000000 rows on any average day. Each line has a (mandatory) batch, it can be 6 different status which is held in the state table. The distribution of status id in the master table is shown below. There is no index on this column, it has a low cardinality, but there are many dml moves in this table. However the State is the main request, the report runs against, so it made a full table scan every time. Users run their applications via an interactive report on Apex 4.0 and it runs slowly. It seemed to be a lock on the $ wwv_FLOW_PREFERENCES caused by this slow execution of interactive report query in this table for and is it locking associated with a slow interactive report query?

  SELECT * from Main_Table where batch =: b2 A full table scan is done in this case. Distribution of status id in the main table 0.12% Reopened pending 1.01% Current 0.17% Pending 0.01% Closed not resolved 96,44% Closed 2.24% Open

  Database Database Oracle 12 c Enterprise Edition Release 12.1.0.2.0 - 64 bit Production PL/SQL Release 12.1.0.2.0 - Production CORE Production 12.1.0.2.0

  AMT for Linux: Version 12.1.0.2.0 - Production

  NLSRTL Version 12.1.0.2.0 - Production

  How about a LIST partition on batch column?

• Oracle Spatial Index on a column NOT NULL

  I'm using the Oracle 11 g with data space init.
  
  I have a SDO_GEOM column in a table that has NULL values for some records. I have to run spatial query based on this column so the need of a spatial index on it. Is it possible to create a Spatial Index on a column SDO_GEOM even if some of them have the NULL value and results of spatial query?
  
  
  Thank you
  Alan
  
  Published by: user3883362 on 29 April 2013 05:59

  Alan,

  Is it possible to create a Spatial Index on a column SDO_GEOM even if some of them are NULL

  Yes.

  SQL> CREATE TABLE test (ID NUMBER PRIMARY KEY, geom MDSYS.SDO_GEOMETRY);
  
  Table created.
  
  -- "insert a row with non-NULL geometry"
  SQL> INSERT INTO test VALUES (1, SDO_GEOMETRY('POINT (6000000 2100000)', 40986));
  
  1 row created.
  
  -- "insert a row with NULL geometry"
  SQL> INSERT INTO test VALUES (2, NULL);
  
  1 row created.
  
  SQL> CREATE INDEX test_spx ON test (geom) INDEXTYPE IS MDSYS.SPATIAL_INDEX;
  
  Index created.
  

  .. .and getting results of spatial query

  Yes, assuming that your data is valid.

  -- "Creates a 10' buffer around the point we previsouly inserted then applies SDO_INSIDE"
  SQL> SELECT ID, SDO_INSIDE(geom, SDO_GEOM.SDO_BUFFER(geom, 10, 1)) FROM test;
  1 TRUE --"our point geometry"
  2 FALSE --"our NULL"
  
  2 rows selected.
  

  If you encounter problems here, I think you can use the functions that are choking in NULL values, for example, the conversion of NULL in WKT geometry.

  How do you access data (sqlplus, application, custom, etc.)? What is the query, and we see a few examples of data?

  Kind regards
  Noel

• decide how to add indexes on the column

  Hi all
  
  I get about confious using index
  
  When should I decide to add index?

  http://docs.Oracle.com/CD/E11882_01/server.112/e25789/indexiot.htm#CNCPT811

  In general, consider creating an index on a column in any of the following situations:
  
      The indexed columns are queried frequently and return a small percentage of the total number of rows in the table.
  
      A referential integrity constraint exists on the indexed column or columns. The index is a means to avoid a full table lock that would otherwise be required if you update the parent table primary key, merge into the parent table, or delete from the parent table.
  
      A unique key constraint will be placed on the table and you want to manually specify the index and all index options.
  

• Indexing of a column based on content types

  Hello
  
  Is it possible to create an index of text only for certain content. For example, I have a table of CONTENTS
  create table CONTENT
  (
  Identification number,
  CONTENT_TYPE_ID number 4,
  Clob DATA
  )
  
  with different content_type_ids say 10, 20, 30, etc. I need to create a text index on the column of DATA for content_type_id = 10. Can anyone help me please with an example? Thanks in advance
  
  Concerning
  REDA

  Another method would be to use the format column in the database using table IGNORE to disregard the documents you do not want to index.

  SQL> alter table CONTENT add fmt varchar2(10);
  
  Table altered.
  
  SQL> update CONTENT set fmt='IGNORE' where  content_type_id != 10;
  
  2 rows updated.
  
  SQL> commit;
  
  Commit complete.
  
  SQL> create index content_idx
   on content (data)
   indextype is ctxsys.context
   parameters ('format column fmt')
  /
  
  Index created.
  

  -Edwin

• unique index on two columns

  Hi all
  I want a unique index on two columns, but when I try this it will show me

    1  CREATE UNIQUE INDEX sale_order_no
    2*   ON sale_order (sale_order_no, season_year)
  SQL> /
    ON sale_order (sale_order_no, season_year)
       *
  ERROR at line 2:
  ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found

  I want to do not overlap with the combination of these two
  
  Plaese Guide
  Thanks and greetings
  Vikas

  You would this behavior if SALE_ORDER_NO has NULL values. If it contains NULL values, a unique single-column index will succeed but an index unique multi-column will fail when it finds duplicates in SEASON_YEAR.

  See:

  SQL> create table dummy_objects (object_id  number, object_owner varchar2(30), object_name varchar2(30));
  
  Table created.
  
  SQL> insert into dummy_objects values (0,'HEMANT','TABLE_A');
  
  1 row created.
  
  SQL> insert into dummy_objects values (1,'HEMANT','TABLE_B');
  
  1 row created.
  
  SQL> insert into dummy_objects values (NULL,'HEMANT','NULL_1');
  
  1 row created.
  
  SQL> insert into dummy_objects values (NULL,'HEMANT','NULL_2');
  
  1 row created.
  
  SQL> create unique index dummy_objects_u1 on dummy_objects(object_id);
  
  Index created.
  
  SQL> drop index dummy_objects_u1;
  
  Index dropped.
  
  SQL> create unique index dummy_objects_u2 on dummy_objects(object_id, object_owner);
  create unique index dummy_objects_u2 on dummy_objects(object_id, object_owner)
                                          *
  ERROR at line 1:
  ORA-01452: cannot CREATE UNIQUE INDEX; duplicate keys found
  
  SQL>
  

  Hemant K Collette
  http://hemantoracledba.blogspot.com

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