What
is an index in SQL?
An index is created in a table to increase the
performance of queries and the data pages are stored contiguously when the
index is created and when the index is new-built.
Index allows us to retrieve very fast data from
the database and allow us to searching millions of records quickly.
How
do database indexes work?
There are some strategies that make indexes work,
1.
Optimize your code.
2.
Restructure your data.
3.
Compress your data.
4.
Materialize them.
5.
Redundancy
How
do indexes help?
For Example, suppose is a student and studying a
book and this book contains 10,000 pages.
In the first day I read some topic “abc” and next
day I want to read some another topic “pqr”. I will never manually go through
page by page. It is very difficult to go
there. In this situation, I am using book index to find specific topic and go
directly to this page because IDEX allow us to search millions of record quickly!
What
types of indexes?
1.
Clustered
3.
Unique
4.
Index with included columns
How
does an index improve performance?
An index is a way to physically re-organise the records
and used to run faster queries.
The index can be used as a pointer to the large
table. It helps to find row quickly and then return back to the user.
What
are some best practices for creating indexes?
Some of the rules are to creating index as,
1.
Index ALL primary keys columns (It is
default).
2.
Index ALL foreign keys columns
3.
You create more indexes only when the
queries are too slow otherwise ignoring it.
The
examples are,
-- CREATE INDEX
CREATE INDEX INDEX_NAME ON TABLE_NAME;
-- CREATE SINGLE COLUMN INDEXE
CREATE INDEX INDEX_NAME ON TABLE_NAME (COLUMN_NAME);
-- CREATE UNIQUE INDEXE
CREATE UNIQUE INDEX INDEX_NAME ON TABLE_NAME (COLUMN_NAME);
-- CREATE COMPOSITE INDEXE
CREATE INDEX INDEX_NAME ON TABLE_NAME (COLUMN_NAME_1, COLUMN_NAME_2);
--DROP INDEX
DROP INDEX INDEX_NAME;
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very much!
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