What is key in mysql

Key in MySQL is an index structure used to quickly find and access data. It stores column values ​​and row pointers, and quickly locates data rows based on column values ​​to improve query performance. MySQL supports multiple Key types, including primary keys, unique keys, ordinary indexes, full-text indexes, and foreign keys.

Key in MySQL

What is Key?

In the MySQL database, Key is an index structure used to quickly find and access data. It stores the values ​​of one or more columns in the data table and the row pointers corresponding to these values.

Types of Key

MySQL supports multiple types of Key, each type has its specific uses and characteristics:

• PRIMARY KEY: Each table can only have one primary key, which forces the column value to be unique and non-null.
• UNIQUE KEY: In addition to the primary key, each table can also have multiple unique keys. The values ​​in a unique key must be unique, but null values ​​are allowed.
• Normal index (INDEX): Normal index does not enforce uniqueness of column values. It simply creates an index on the column, making finding data faster.
• Full-text index (FULLTEXT): Full-text index is used for fast search of text fields and supports natural language queries.
• Foreign key (FOREIGN KEY): Foreign key is used to establish a relationship between two tables. It refers to the primary key or unique key of another table.

The role of Key

The main role of Key is to improve query performance by quickly finding data:

• Index allows MySQL Navigate directly to specific rows of a data table without scanning the entire table. This can significantly reduce query time.
• Key can also help MySQL optimize query plans and select the most effective execution strategy.

Create Key

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

<code>CREATE INDEX index_name ON table_name (column_name);</code>

To delete Key

you can use the DROP INDEX statement to delete Key:

<code>DROP INDEX index_name ON table_name;</code>

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