What is index and explain its purpose

What is index and explain its purpose.

An index is typically used to retrieve records of a table at a faster rate. This is because an index contains value of the indexed column.

Example:
The example below creates an index student_idx in table student for column student_name
CREATE INDEX student_idx
       ON student (student_name);

What is index and explain its purpose.

- An index is a pointer to a location of data.

- The purpose of an index is to make SQL queries run faster.

- If the optimizer detects an index that matches part of the WHERE clause of the query, then it uses the index to avoid having to read every row in the table.
What are the guidelines to decide which table s to index?
On rebuilding an Index, the existing index is dropped and a new one is built. This operation can consume a lot of time and resources......
What are the guidelines to decide which column to index?
Non-key columns can be dropped from a table only after the non-key index is dropped first...
What is composite index?
What is composite index? - A composite index contains more than one key column.....
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