Topic: SQL*Plus and PL/SQL >> Nonunique index doubt
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| Title: Nonunique index doubt |
| muzu |
Posted: Aug 21, 2007 12:55:38 PM |
Total Post: 37
Joined: Aug, 2007
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How a nonunique index works ?
When and where it is mainly used ?
can any one explain with an example. |
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 muzu |
| Posted: Aug 22, 2007 01:49:54 AM |  |
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Total Post: 37
Joined: Aug, 2007
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Also one more issue with this example
If I have a table t1 with a column a as follows
A
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
if i create a non unique index on column A of table t1
and access a row by giving the following select statement
select a from t1 where a > 1;
where we get all the values that are '2' returning 10 rows.
Here the non-unique index goes with index range scan.
1) Is it that it also takes the rowid into account while accessing the row values of 2 ?
2) Suppose if i want a particular row value from a particular position say for example 12th position in the column A. How can non-unique index will be useful and how it actually accesses and what will be the query?
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