When should you create an index?

Question

Index the Correct Tables and Columns Create an index if you frequently want to retrieve less than about 15% of the rows in a large table. This threshold percentage varies greatly, however, according to the relative speed of a table scan and how clustered the row data is about the index key.

Why would you create an index?

Indexes are used to retrieve data from the database more quickly than otherwise. The users cannot see the indexes, they are just used to speed up searches/queries. Note: Updating a table with indexes takes more time than updating a table without (because the indexes also need an update).

When should I use index in database?

An index in a database is very similar to an index in the back of a book. It means when we want to jump to a specific topic from a book then we can first see the index of the book and then find the page number for that topic and then open that topic by going to that page number.

When should you not add an index?

As a general rule, you do not want to use an index on a column used in a query's condition that will return a high percentage of data rows from the table. In other words, do not create an index on a column such as gender, or any column that contains very few distinct values.

What are the conditions to create an index?

To create an index in your own schema, one of the following conditions must be true:The table or cluster to be indexed must be in your own schema.You must have the INDEX object privilege on the table to be indexed.You must have the CREATE ANY INDEX system privilege.CREATE INDEX

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