Create index

Definition

Create index is a command used in database management systems to improve the speed and efficiency of data retrieval operations. By creating an index on one or more columns of a table, the database can quickly locate and access the required records without having to search through every row, which enhances performance for queries, especially on large datasets.

5 Must Know Facts For Your Next Test

1. Creating an index can significantly speed up query performance, especially for search operations and joins, but it can slow down data modification operations like inserts and updates due to the additional overhead of maintaining the index.
2. Indexes can be created on single or multiple columns, allowing for flexible query optimizations based on the specific needs of data retrieval.
3. There are various types of indexes, such as unique indexes, composite indexes, and full-text indexes, each serving different use cases and improving performance in distinct ways.
4. The command `CREATE INDEX` is often followed by specifying the index name, the table name, and the columns to be indexed in SQL syntax.
5. Indexes consume additional disk space, which can be a consideration when deciding how many and what types of indexes to create in a database.

Review Questions

• How does creating an index improve query performance in a database?
  • Creating an index improves query performance by allowing the database to quickly locate and access specific records without scanning the entire table. This is particularly beneficial for large datasets where searching through every row would be time-consuming. Indexes act as pointers that help speed up data retrieval operations, making queries execute faster.
• What are some potential downsides to creating indexes in a database system?
  • While indexes can enhance retrieval performance, they can also introduce downsides such as increased disk space usage and slower performance for data modification operations like inserts, updates, and deletes. Each time data is modified, any associated indexes must also be updated, leading to additional overhead. Therefore, it's essential to balance the benefits of indexing against its impact on overall database performance.
• Evaluate how different types of indexes, such as clustered and non-clustered indexes, affect data retrieval strategies in databases.
  • Different types of indexes play critical roles in shaping data retrieval strategies. A clustered index determines the physical order of data storage in a table, making it highly efficient for range queries. In contrast, non-clustered indexes maintain a separate structure that references the original data but does not alter its physical order. This allows for quicker lookups but may require more disk space. Understanding these differences helps database designers optimize query performance based on specific access patterns and requirements.

Related terms

Primary Key: A unique identifier for a record in a database table that ensures each entry is distinct.

Query Optimization: The process of enhancing the performance of database queries by analyzing and improving their execution plans.

Clustered Index: An index that determines the physical order of data in a table, meaning there can be only one clustered index per table.