Table indexing is a technique used to improve the performance of database queries. An index is a data structure that allows faster retrieval of records based on the values in one or more columns of a table. It works like the index of a book, where you can quickly locate information by looking up a keyword in the index rather than reading the entire book.
In this article, we will discuss the importance of indexing in a database, the types of indexes, how to create an index in MySQL, and some best practices to follow when indexing tables.
Why is indexing important?
When you query a large table without an index, the database engine has to scan the entire table to find the relevant records, which can take a long time. However, if you create an index on the columns used in the query, the database engine can use the index to locate the relevant records much faster.
The benefits of indexing include:
Faster query performance: Indexing allows the database engine to quickly locate and retrieve the relevant records, resulting in faster query performance.
Reduced disk I/O: With indexing, the database engine can access the required data pages directly without having to read the entire table, reducing disk I/O.
Improved concurrency: Indexing can improve concurrency by reducing the time required to read and write data to the table.
Types of indexes
There are several types of indexes, including:
Primary index: A primary index is a unique index created on the primary key column(s) of a table. It ensures that each row in the table is uniquely identified and can be used as a reference to link with other tables.
Unique index: A unique index is an index that ensures that the values in a column or a group of columns are unique. It is similar to a primary index but can be created on non-primary key columns.
Non-unique index: A non-unique index is an index that allows duplicate values in the indexed columns. It is used to speed up queries that involve searching or sorting data.
Composite index: A composite index is an index that is created on multiple columns. It is used to speed up queries that involve searching or sorting data based on multiple criteria.
Creating an index in MySQL
To create an index in MySQL, you can use the CREATE INDEX statement. Here’s an example:
CREATE INDEX index_name ON table_name (column_name);
In this example,
index_name is the name of the index,
table_name is the name of the table, and
column_name is the name of the column on which you want to create the index.
You can also create a composite index by specifying multiple columns in the CREATE INDEX statement, like this:
CREATE INDEX index_name ON table_name (column1, column2, ...);