search
HomeDatabaseMysql TutorialWhat are the keywords of primary key in mysql

In MySQL, use the PRIMARY KEY keyword to specify the primary key. The primary key is a field or field combination that uniquely identifies each row of records. It is unique (the primary key value is different for each row) and non-null (the primary key value is different). is NULL) property. Additionally, define the primary key using the following syntax: CREATE TABLE table_name ( column_name1 DATA_TYPE PRIMARY KEY, ... ).

What are the keywords of primary key in mysql

Keywords for primary key in MySQL

In MySQL, the keyword used to specify the primary key isPRIMARY KEY.

Definition of primary key

The primary key is a field or combination of fields that uniquely identifies each row of records in a database table. It has the following properties:

  • Uniqueness: Primary key values ​​are unique for all rows in a given table.
  • Non-null: The primary key cannot be a NULL value.

Use the PRIMARY KEY keyword

To designate one or more fields as the primary key, use the PRIMARY KEY keyword when creating the table, as follows Display:

CREATE TABLE table_name (
  column_name1 DATA_TYPE PRIMARY KEY,
  column_name2 DATA_TYPE,
  ...
);

where:

  • table_name is the name of the table.
  • column_name1 is the name of the primary key field.
  • DATA_TYPE Specifies the data type of the field.

Example

The following example creates a table named customers where customer_id is the primary key:

CREATE TABLE customers (
  customer_id INT PRIMARY KEY,
  name VARCHAR(255),
  email VARCHAR(255)
);

In the above example, the customer_id field is unique and non-null, which means that no two rows in the table have the same customer_id value, and customer_id The value is never NULL.

The above is the detailed content of What are the keywords of primary key in mysql. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
MySQL's Role: Databases in Web ApplicationsMySQL's Role: Databases in Web ApplicationsApr 17, 2025 am 12:23 AM

The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.

MySQL: Building Your First DatabaseMySQL: Building Your First DatabaseApr 17, 2025 am 12:22 AM

The steps to build a MySQL database include: 1. Create a database and table, 2. Insert data, and 3. Conduct queries. First, use the CREATEDATABASE and CREATETABLE statements to create the database and table, then use the INSERTINTO statement to insert the data, and finally use the SELECT statement to query the data.

MySQL: A Beginner-Friendly Approach to Data StorageMySQL: A Beginner-Friendly Approach to Data StorageApr 17, 2025 am 12:21 AM

MySQL is suitable for beginners because it is easy to use and powerful. 1.MySQL is a relational database, and uses SQL for CRUD operations. 2. It is simple to install and requires the root user password to be configured. 3. Use INSERT, UPDATE, DELETE, and SELECT to perform data operations. 4. ORDERBY, WHERE and JOIN can be used for complex queries. 5. Debugging requires checking the syntax and use EXPLAIN to analyze the query. 6. Optimization suggestions include using indexes, choosing the right data type and good programming habits.

Is MySQL Beginner-Friendly? Assessing the Learning CurveIs MySQL Beginner-Friendly? Assessing the Learning CurveApr 17, 2025 am 12:19 AM

MySQL is suitable for beginners because: 1) easy to install and configure, 2) rich learning resources, 3) intuitive SQL syntax, 4) powerful tool support. Nevertheless, beginners need to overcome challenges such as database design, query optimization, security management, and data backup.

Is SQL a Programming Language? Clarifying the TerminologyIs SQL a Programming Language? Clarifying the TerminologyApr 17, 2025 am 12:17 AM

Yes,SQLisaprogramminglanguagespecializedfordatamanagement.1)It'sdeclarative,focusingonwhattoachieveratherthanhow.2)SQLisessentialforquerying,inserting,updating,anddeletingdatainrelationaldatabases.3)Whileuser-friendly,itrequiresoptimizationtoavoidper

Explain the ACID properties (Atomicity, Consistency, Isolation, Durability).Explain the ACID properties (Atomicity, Consistency, Isolation, Durability).Apr 16, 2025 am 12:20 AM

ACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.

MySQL: Database Management System vs. Programming LanguageMySQL: Database Management System vs. Programming LanguageApr 16, 2025 am 12:19 AM

MySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.

MySQL: Managing Data with SQL CommandsMySQL: Managing Data with SQL CommandsApr 16, 2025 am 12:19 AM

MySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Chat Commands and How to Use Them
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

ZendStudio 13.5.1 Mac

ZendStudio 13.5.1 Mac

Powerful PHP integrated development environment

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version