SQL Concept- Part 1

 

In this blog we are going to understand the important and basic concepts of SQL...

1.How to cretate a SQL Server database connection and new database?

firstly open SSMS and connect with server also ensure SQL server is in running mode.

create a new database:

                                        

create a table:

                                          

2.What is Primary key in SQL Server?

• The PRIMARY KEY constraint uniquely identifies each record in a table.
• Primary key always has unique data.
• A primary key cannot have null value.
• There can be no duplicate value for a primary key.

   

  

3.What is an identify column in SQL Server?

  

• Identity column of a table is a column whose value increases automatically. 
• The value in an identity column is created by the server. 
• A user generally cannot insert a value into an identity column. 

 

4.How we can create primary key and foreign key relationship?

• Choose the primary key of table tblCustomer and make relationship with another tablet tblAddress1.
• To make so goto table tblAddress1 design ->right click on it->Choose an option called relationship->Click on Add We will get dialog box as below. 
• Choose your foreign key which is primary key of another table called tblCustomer.

                                          

5.Are nulls allowed in foreign key?

    

             Yes, it can be NULL or duplicate. 

Example:

                                               

Output:

        

For more understanding watch below video :

https://youtu.be/uGlfP9o7kmY

Thank you!!!!