Usage of key in mysql

MySQL's Key is an index used to quickly find data, speed up queries and improve performance. It comes in different types including primary key, unique key, normal index, composite index and full text index. Keys can be created using the CREATE INDEX statement. Choosing the right Key is critical to optimizing queries, taking into account common query patterns, range searches, and table update frequency.

Key usage in MySQL

What is Key?

Key is a special index in a MySQL table used to quickly find specific data. It speeds up queries by creating internal data structures that reference specific columns or combinations of columns in a table.

Why use Key?

Using Key has the following benefits:

• Improving query speed: Key allows MySQL to directly access specific rows in the table without scanning the entire table .
• Reduced I/O operations: By accessing only relevant rows, Key reduces disk I/O operations, thereby improving performance.
• Enforce uniqueness: A unique key ensures that there are no duplicate rows in the table.
• Optimizing related queries: Foreign keys are used to associate different tables, and Key can optimize these queries.

Key type

MySQL supports multiple types of Key:

• Primary key: in the table A unique key that identifies a unique row. One or more columns can make up the primary key.
• Unique key: Similar to primary key, but allows NULL values ​​in the table.
• Normal index: Used to speed up queries, but allows duplicate values.
• Compound index: An index created across multiple columns.
• Full-text index: Used to search for keywords in text columns.

Create Key

You can use the CREATE INDEX statement to create a Key:

CREATE INDEX index_name ON table_name (column_name);

For example, for Create a common index on the name column of the users table:

CREATE INDEX name_index ON users (name);

Choose the appropriate Key

Choosing the appropriate Key is crucial, Because it affects query performance. Here are some guidelines:

• Select columns that are frequently used in queries.
• Create indexes for columns that are frequently range searched.
• If the table is updated frequently, avoid creating indexes.
• A composite index should contain columns from different tables that are joined.

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