What does primary key mean in mysql?

The primary key is a special column or combination of columns in a MySQL table that ensures the uniqueness and integrity of each row. It provides the following functions: Uniqueness guarantee: the primary key value is unique for each row, preventing duplication. Fast query: Create index on primary key to speed up data search. Data integrity: Foreign key constraints rely on the primary key to ensure the integrity of the associated table data.

What is a primary key in MySQL?

The primary key is a special column or combination of columns that uniquely identifies each row in a MySQL table. It is essential to ensure the integrity and uniqueness of the data in the table.

The role of the primary key:

• Uniqueness guarantee: The primary key value must be unique for each row in the table. This Meaning no two rows can have the same primary key value.
• Fast Query: MySQL uses the primary key to quickly find data in a table because it creates an efficient index that enables the database engine to skip searching the entire table.
• Data integrity: Foreign key constraints rely on the primary key to ensure data integrity. Primary keys prevent accidental changes to related tables when an update or delete operation results in a violation of a foreign key constraint.

Creation of primary key:

You can use the PRIMARY KEY constraint of the CREATE TABLE statement to create a primary key . For example:

<code>CREATE TABLE products (
  id INT NOT NULL AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  PRIMARY KEY (id)
);</code>

In this case, the id column is designated as the primary key. It is an auto-incrementing integer, which ensures that each row has a unique and sequential value.

Types of primary keys:

MySQL supports different primary key types:

• Simple primary key: A single column acts as Primary key.
• Composite primary key: A combination of multiple columns acts as a primary key.

Select a primary key:

When selecting a primary key, consider the following factors:

• Uniqueness: Column values ​​should be unique in the table.
• Immutability: Column values ​​should rarely or never change.
• Quick Query: Column values ​​should be easy to search and sort.

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