Objectives

Upon completion of this lesson, you will be able to:

  • build an index for a non-prime column in a relational database

Overview

Indexing methods in Relational Database Management Systems (RDBMS) are crucial for enhancing the performance of data retrieval operations without the need to scan the entire table. Indexes provide a faster path to access data based on the values of one or more columns. There are several indexing methods commonly used by RDBMS:

  1. B-Tree Indexes:
    • The most common type of index used in databases.
    • They store data in a balanced tree structure, allowing for efficient searching, insertion, deletion, and updating operations.
    • B-Tree indexes can be used for equality and range queries effectively.
  2. Hash Indexes:
    • Based on hash tables, hash indexes are very efficient for equality searches that match the indexed columns exactly.
    • Not suitable for range queries because the order of data is not preserved.
    • Mainly used in scenarios where quick lookup of records is required.
  3. Composite (Multi-Column) Indexes:
    • Combine two or more columns in a single index structure.
    • Useful when queries frequently filter or sort on multiple columns.
    • The order of columns in the index is important for its effectiveness.
  4. Bitmap Indexes:
    • Store index data as a set of bits in a bitmap for each distinct value of the indexed column.
    • Highly efficient for queries involving equality, especially on columns with a low cardinality (i.e., having few unique values).
    • Particularly useful for data warehousing scenarios where aggregate functions are common.
  5. Full-Text Indexes:
    • Designed to support the searching of text data within columns.
    • Can efficiently handle queries that contain words or phrases, making them ideal for searching large text fields.
    • Use specialized algorithms to index the content of text-based columns, allowing for complex text search queries.
  6. Spatial Indexes:
    • Used for indexing spatial data, such as geographical coordinates, maps, and geometry objects.
    • Support efficient querying of spatial objects like finding all locations within a given distance or region.
    • Typically implemented using data structures such as R-trees or Quad-trees.

Each indexing method has its specific use cases, advantages, and limitations. The choice of index depends on the nature of the data, the types of queries frequently executed, and the performance requirements of the database system. Effective use of indexes can significantly reduce query response times and improve the overall performance of a database system.

Summary

References

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Errata

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