SQL CREATE INDEX Statement
SQL CREATE INDEX Statement
In SQL, the CREATE INDEX statement is used to create an index on one or more columns of a table. An index is a data structure that allows for faster searching and sorting of data in a table.
Here is an example of how to create an index in SQL:
CREATE INDEX idx_name ON customers (last_name, first_name);
In this example, we are creating an index called “idx_name” on the “last_name” and “first_name” columns of the “customers” table. The CREATE INDEX statement specifies the name of the index, the name of the table, and the columns to be indexed.
After an index is created, it can be used by the database to speed up queries that involve searching or sorting data based on the indexed columns. For example, if we have the following query:
SELECT * FROM customers WHERE last_name = ‘Smith’;
If an index exists on the “last_name” column, the database can use the index to quickly find all rows where the last name is “Smith”, rather than scanning the entire table.
It is important to note that while indexes can improve query performance, they also come with some drawbacks. Indexes take up additional storage space and can slow down write operations (such as inserts, updates, and deletes) because the database must update the index as well as the table. Therefore, it is important to carefully consider which columns to index and to monitor the performance of queries over time to ensure that the indexes are providing a net benefit.