Overview
Let’s learn about the primary key in this tutorial. The database needs a unique way to identify each record in the database table. The purpose of the primary key is to ensure data integrity and to enable efficient retrieval of data from the database table.
Primary Key
A primary key is a unique identifier that is used to uniquely identify each record or row in a database table. It is a column or set of columns in a table that is used to uniquely identify each record in the table. The primary key must be unique and cannot contain null values.
There can only be one primary key in a table, but a primary key can use multiple fields. Note that the column/s used as a primary key cannot contain null values.
Users can specify the primary key in the table. For example, MySQL users can specify by using the PRIMARY KEY constraint.
The database can automatically create primary key values in the table. For example, MS Access can automatically create the primary key for you, Access will add an autonumber field that will assign a unique number to each record that you create.
Use
The primary key is used for relationships between tables in a database. When a table is joined to another table, the primary key of the first table is used as a foreign key in the second table. This creates a link between the two tables that can be used to retrieve data from both database tables.
MySQL Example
In MySQL database, a PRIMARY KEY constraint is used to define a primary key for the table. We can either specify during table creation or add the primary key to the existing table by modifying the table using the ALTER TABLE command.
CREATE TABLE sample_table_name (
column_1 datatype PRIMARY KEY,
column_2 datatype,
…
);
In this syntax, column_1 is the name of the column that you want to use as the primary key, and datatype is the data type of the column.
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MySQL Tutorials
MySQL Tutorials on this website:
https://www.testingdocs.com/mysql-tutorials-for-beginners/
For more information on MySQL Database: