ramiya

• May 7th, 2006

 

helloi have doubt in where i used create index and unique index.plz replay it immediately

Ajeet Singh

• May 21st, 2006

 

We should create an index if a column contains a wide range of values, a column contains a large number of null values, one or more columns are frequently used together in a WHERE clause or a join condition and the table is large and most queries are expected to retrieve less than 2-4% of the row.

Format of Create Index:

Create Index emp_last_name_idx ON emp (dept_id);

If you want to exforce uniqunes, you should define a unique or primary key constraint in the table definition. then a unique index is created automatially.

Constraint emp_email_uk UNIQUE(email);

kanak3

 Profile Answers by kanak3 

• Jun 27th, 2007

 

Indexes can be unique or nonunique. Unique indexes guarantee that no two rows of a table have duplicate values in the key column (or columns). Nonunique indexes do not impose this restriction on the column values.

Sant_parkash

 Profile Answers by Sant_parkash Questions by Sant_parkash

• Jan 31st, 2008

 

Index will only help you in searching the data but unique index will provide uniqueness to the indexed column. But in both the cases NULL values are allowed to insert.

JP

• May 25th, 2014

 

When create primary constraints oracle automatically creates Unique Index .
Using "Create index" by default oracle will create B tree index .
To create other indexes like Bit map,IOT index you need mention the Index name while creating index
ex "create Bitmap index "