Creating a table, creating a primary key is a good habit or should be used as a norm. If it is predicted that a large amount of data may be accumulated, the primary key must be set, and the appropriate primary key should be selected, otherwise you will seriously affect the count query, insert, and delete. The following article will introduce to you what a primary key is in MySQL and what its use is. I hope it will be helpful to you.
#What is a primary key?
The database primary key refers to a column or a combination of multiple columns whose value can uniquely identify each row in the table, through which the entity integrity of the table can be enforced. The primary key is mainly used for foreign key association with other tables, as well as modification and deletion of this record.
Primary key (primary key) A column (or a group of columns) whose value uniquely distinguishes each row in the table.
This column (or this group of columns) that uniquely identifies each row in the table is called the primary key. Without a primary key, updating or deleting specific rows in a table is difficult because there is no safe way to ensure that only relevant rows are designed.
Although a primary key is not always required, most database designers should ensure that every table they create has a primary key to facilitate future data manipulation and management
Any column can be used as a primary key, as long as it meets the following conditions:
1. No two rows have the same primary key value
2. Each row must have a primary key value (NULL values are not allowed in primary key columns)
What is the use of primary key?
The primary key is a unique identifier that can determine a record, and is mainly used to determine the uniqueness of the data. The primary key field must be unique and non-empty. There can be only one primary key in a table, and the primary key can contain one or more fields.
For example, a record includes identity number, name, age, school, nationality, gender, etc. The ID number is the only one that can identify you. Others may be duplicated. Therefore, the ID number is the primary key.
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