The role of indexes in databases

Database index improves search and retrieval speed by creating an array of pointers pointing to data. Its functions include: improving search speed, supporting sorting and grouping, providing unique constraints, optimizing range queries, and reducing lock conflicts

The role of database index

A database index is a data structure that helps quickly find and retrieve records in a database. It works by creating an array of pointers to data table records, sorting the pointers based on the value of a specified column.

The role of index:

• #Improve search speed:The index allows the database server to jump directly to the data page containing the target record, and No need to scan the entire table sequentially. This greatly improves lookup speed, especially in large data tables.
• Support sorting and grouping: Indexes can be used to sort and group data without reordering the entire table. This significantly improves the performance of queries involving these operations.
• Uniqueness constraints: Indexes can force certain columns of the data table to have unique values, thereby preventing duplicate records.
• Range query optimization: Indexes can optimize queries involving range queries, such as finding records within a specific value range.
• Reduce lock conflicts: Indices can help reduce lock conflicts because they allow the database server to skip data pages that do not contain the target record.

How it works:

When an index is created on a column, the database creates a balanced tree-like structure called a B-tree. Each node in the B-tree contains a pointer to a data page, as well as a key value used to move from one node to another.

When executing a query, the database server will first check the index and find the corresponding node based on the value used in the query. It then follows the pointer to the data page containing the target record and retrieves the record from it.

Note:

• Creating an index will occupy storage space.
• Maintaining indexes requires additional overhead and may affect the performance of write operations.
• Not all queries benefit from indexes. Indexes are only effective if the query involves a large number of search or sort operations.

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