search
HomeDatabaseMysql TutorialWhat does the identity attribute in SQL mean?

What does the identity attribute in SQL mean?

What is Identity in SQL, specific code examples are needed

In SQL, Identity is a special data type used to generate auto-incrementing numbers, it is commonly used To uniquely identify each row of data in the table. The Identity column is often used in conjunction with the primary key column to ensure that each record has a unique identifier. This article will detail how to use Identity and some practical code examples.

  1. Basic usage of Identity

When creating a table, you can use the Identity attribute to specify a column as an auto-increment column. Typically, the Identity column is used with an integer type (such as INT, BIGINT, etc.). The following is an example of using Identity when creating a table:

CREATE TABLE [dbo].[Customers]  (
   [CustomerID] INT IDENTITY(1,1) PRIMARY KEY,
   [CustomerName] NVARCHAR(50) NOT NULL,
   [ContactName] NVARCHAR(50) NOT NULL,
   [Address] NVARCHAR(100) NULL
);

In the above code, the CustomerID column is designated as the Identity column. Each time data is inserted, it will automatically generate a unique auto-incrementing number as an identification .

  1. Attributes of Identity

The Identity column has two important attributes: Seed (seed) and Increment (increment).

Seed specifies the starting value of the Identity column, which defaults to 1. In the above example, the Seed value is 1, which means that the CustomerID of the first row of data is 1, the CustomerID of the second row of data is 2, and so on.

Increment specifies the growth step of the Identity value, and the default is 1. In the above example, the Increment value is 1, which means that every time new data is inserted, the Identity value will automatically increase by 1. However, you can also change the growth step size by modifying the Increment value.

  1. Inserting data using Identity

Inserting data using the Identity column is very simple, just do not include the value of the Identity column. When inserting data, the database automatically generates unique values ​​for the Identity column. The following example shows how to insert data into the Identity column:

INSERT INTO Customers (CustomerName, ContactName, Address)
VALUES ('ABC Company', 'John Smith', '123 Main Street');

INSERT INTO Customers (CustomerName, ContactName, Address)
VALUES ('XYZ Inc', 'Jane Doe', '456 Maple Avenue');

In the above code, we only inserted the values ​​of the CustomerName, ContactName and Address columns without specifying the value of CustomerID. The database automatically generates a unique value for CustomerID.

  1. Get the value of Identity

Sometimes, we need to get the Identity value of the data we just inserted. In SQL Server, we can use the SCOPE_IDENTITY() function to obtain the Identity value of the most recently inserted data. The following code shows how to use the SCOPE_IDENTITY() function:

INSERT INTO Customers (CustomerName, ContactName, Address)
VALUES ('ABC Company', 'John Smith', '123 Main Street');

SELECT SCOPE_IDENTITY() AS LastID;

In the above code, we insert a new piece of data and use the SELECT statement to obtain the Identity value of the recently inserted data, which is stored in the LastID field middle.

  1. Customize the Identity column

Sometimes, we may want to customize the starting value of the Identity column. SQL Server allows us to modify the current value of the Identity column through the DBCC CHECKIDENT statement. The following code shows how to use the DBCC CHECKIDENT statement:

DBCC CHECKIDENT ('Customers', RESEED, 100);

In the above code, we reset the current value of the Identity column of the Customers table to 100. The next time data is inserted, the Identity value will increment from 101.

Summary:

Identity is a commonly used auto-increment identifier in SQL, used to identify the uniqueness of each row of data in the table. When creating a table, you can use the Identity property to specify a column as the Identity column. When inserting data, if the value of the Identity column is not specified, the database will automatically generate a unique self-increasing number as an identifier. Through the SCOPE_IDENTITY() function, you can get the Identity value of the most recently inserted data. At the same time, you can use the DBCC CHECKIDENT statement to customize the current value of the Identity column. I hope this article will be helpful for you to study and use Identity in SQL.

The above is the detailed content of What does the identity attribute in SQL mean?. 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
SQL Server使用CROSS APPLY与OUTER APPLY实现连接查询SQL Server使用CROSS APPLY与OUTER APPLY实现连接查询Aug 26, 2022 pm 02:07 PM

本篇文章给大家带来了关于SQL的相关知识,其中主要介绍了SQL Server使用CROSS APPLY与OUTER APPLY实现连接查询的方法,文中通过示例代码介绍的非常详细,下面一起来看一下,希望对大家有帮助。

SQL Server解析/操作Json格式字段数据的方法实例SQL Server解析/操作Json格式字段数据的方法实例Aug 29, 2022 pm 12:00 PM

本篇文章给大家带来了关于SQL server的相关知识,其中主要介绍了SQL SERVER没有自带的解析json函数,需要自建一个函数(表值函数),下面介绍关于SQL Server解析/操作Json格式字段数据的相关资料,希望对大家有帮助。

聊聊优化sql中order By语句的方法聊聊优化sql中order By语句的方法Sep 27, 2022 pm 01:45 PM

如何优化sql中的orderBy语句?下面本篇文章给大家介绍一下优化sql中orderBy语句的方法,具有很好的参考价值,希望对大家有所帮助。

Monaco Editor如何实现SQL和Java代码提示?Monaco Editor如何实现SQL和Java代码提示?May 07, 2023 pm 10:13 PM

monacoeditor创建//创建和设置值if(!this.monacoEditor){this.monacoEditor=monaco.editor.create(this._node,{value:value||code,language:language,...options});this.monacoEditor.onDidChangeModelContent(e=>{constvalue=this.monacoEditor.getValue();//使value和其值保持一致i

一文搞懂SQL中的开窗函数一文搞懂SQL中的开窗函数Sep 02, 2022 pm 04:55 PM

本篇文章给大家带来了关于SQL server的相关知识,开窗函数也叫分析函数有两类,一类是聚合开窗函数,一类是排序开窗函数,下面这篇文章主要给大家介绍了关于SQL中开窗函数的相关资料,文中通过实例代码介绍的非常详细,需要的朋友可以参考下。

springboot配置mybatis的sql执行超时时间怎么解决springboot配置mybatis的sql执行超时时间怎么解决May 15, 2023 pm 06:10 PM

当某些sql因为不知名原因堵塞时,为了不影响后台服务运行,想要给sql增加执行时间限制,超时后就抛异常,保证后台线程不会因为sql堵塞而堵塞。一、yml全局配置单数据源可以,多数据源时会失效二、java配置类配置成功抛出超时异常。importcom.alibaba.druid.pool.DruidDataSource;importcom.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;importorg.apache.

Monaco Editor怎么实现SQL和Java代码提示Monaco Editor怎么实现SQL和Java代码提示May 11, 2023 pm 05:31 PM

monacoeditor创建//创建和设置值if(!this.monacoEditor){this.monacoEditor=monaco.editor.create(this._node,{value:value||code,language:language,...options});this.monacoEditor.onDidChangeModelContent(e=>{constvalue=this.monacoEditor.getValue();//使value和其值保持一致i

如何使用exp进行SQL报错注入如何使用exp进行SQL报错注入May 12, 2023 am 10:16 AM

0x01前言概述小编又在MySQL中发现了一个Double型数据溢出。当我们拿到MySQL里的函数时,小编比较感兴趣的是其中的数学函数,它们也应该包含一些数据类型来保存数值。所以小编就跑去测试看哪些函数会出现溢出错误。然后小编发现,当传递一个大于709的值时,函数exp()就会引起一个溢出错误。mysql>selectexp(709);+-----------------------+|exp(709)|+-----------------------+|8.218407461554972

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)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools