#unique key

[dntdrifts]

In SQL Server, we have two keys which distinctively or uniquely identify a record in the database. Both the keys seem identical, but actually, both are different in features and in behaviours. In this article, I would like to share the key differences between primary key and unique key.

[instantpapermagazine]

Difference Between Primary Key and Unique Key - Comment Sensortir

A composite primary key, it should be defined at the table level. Let's learn the Difference between primary key and unique key.

[saitorhan]

Kolon Seviyesinde Veri Bütünlüğünü Sağlamak

Kolon seviyesinde tanımlanan şartlar (constraint) aynı tablo içerisinde kolonda yer alan değerlerin tutarlılığını sorgular.

Kolon seviyesinde veri bütünlüğü sağlama yollarını inceleyelim;

Primary Key:

Normalizayon kuralları gereği her tabloda en az bir anahtar alan bulunmak zorundadır. Tanımlanan bu anahtar alan primary key olarak tanımlanır ve NULLdeğer kabul etmeyen tekil bir anahtardır. Tablo…

View On WordPress

[sandeep2363]

Constraints in database

Explanation of Constraints:

Not Null The NOT NULL constraint enforces a column to NOT accept NULL values. This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field.

Example

Primary Key The PRIMARY KEY constraint uniquely identifies each record in a database table. Primary keys must contain UNIQUE…

View On WordPress

[essentialsql]

What is the difference between a primary and unique key?

What is the difference between a primary and unique key?

In this article we learn the difference between a primary and unique key, and why both are important to maintaining a relational database structure. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these free tools using my Guide Getting Started Using SQL Server.

Before we get into the difference,…

View On WordPress