• Introduction
  • 1. How to Retrieve Data From a Single Table
  • 2. How to Retrieve Data from Multiple Tables
  • 3. Using Functions
  • 4. How to Insert, Update, Delete Data in Tables
  • 5. Summary Queries and Aggregate Functions
  • 6. Working With Subqueries
  • 7. SQL Views
  • 8. SQL Indexes
  • Glossary
  • Index
  • Download
  • Translations
  • 8.1

    SQL Indexes Explained

    SQL Indexes

    • You can create SQL indexes from single or multiple columns.
    • A SQL index is like the index of a book. It speeds up the retrieval of a record. The relational database management system (RDBMS) can retrieve a record with the index key instead of having to perform a table scan.
    • MySQL automatically creates indexes for primary and foreign keys significantly speeding up join performance.
    • You should only create indexes on columns used in a join or search because the RDMS must update an index every time you execute an INSERT, UPDATE, or DELETE.

    When to Create an Index

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