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 ? Are the non-unique index values are unique ?
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?
3) When and where the non-unique indexes are mainly used ?
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 ? Are the non-unique index values are unique ?
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?
3) When and where the non-unique indexes are mainly used ?