SQL Delete Cascade and Update Cascade with foreign key

SQL-DELETE-CASCADE
SQL Delete Cascade rule

In this article, we will learn SQL Delete Cascade rules with foreign key constraints having multiple examples.

SQL Delete CascadeOverview

1.  SQL DELETE CASCADE : In the SQL server, when we create a foreign key using the SQL delete cascade option, it deletes all the related rows from the child table when the referenced row is deleted from the parent table having primary key constraint.

The following are the SQL scripts that create a parent (Departments), child (Employees) table, and a foreign key on the child table without the SQL delete cascade rule.

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Primary Key Constraint In SQL Server

The  PRIMARY KEY  constraint in SQL Server ensures that each entry in a table is uniquely recognized.
Primary keys must have UNIQUE values and cannot have NULL values.
In SQL Server, a table can only have one primary key, which can be made up of one or more columns (fields).

What is the primary key in SQL Server?

In SQL Server, a  Primary Key  is a field or column which uniquely identifies each and every record in a table.

    • A primary key column doesn’t allow to insert  null  or duplicate values.
    • A Primary key can consist of up to 16 columns.
    • A table can have only one primary key which can be applied on single or multiple columns.
    • The primary key consist of multiple columns or fields is known as the Composite primary key.
    • A Primary Key constraint can be applied to the columns having any data types.
    • A primary key by default creates a clustered index on the column.

A primary key can be created at the column or table level.

Primary Key Constraint  in SQL Server
Primary Key Constraint in SQL Server

Syntax to create a primary key

The following are the syntax to create a primary key in SQL server.

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CREATE, ALTER, AND DROP DATABASE IN SQL SERVER

In this article, we will discuss how to Create, Alter, and Drop a database in SQL Server.
In my previous article, we have discussed all about the Types of SQL Commands.

Database Introduction

 Database  : In the SQL server a database is a place to store the data in an electronic format. It is an organized collection of database objects such as tables, views, functions, stored procedures, triggers and so on.
It allows a user to easily access or manipulate the data.

SQL server database

Create Database In SQL Server

In SQL Server, there are two ways to create a user-defined database, either by using the Transact-SQL statements or by using SQL Server Management Studio.

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5 Types of SQL Commands: DDL, DML, DCL, TCL, and DQL Commands

In this article, we’ll go through how to create a database in SQL Server and try and understand the different types of SQL commands. The SQL programming language supports a number of commands to perform different operations such as DCL, TCL, DQL, DDL, and DML Command.

Among other things, SQL commands can be used to create a database, create tables, add data to tables, drop tables, Alter tables, and provide access to users.

image-types of SQL Commands
Types of SQL Commands

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