SQL Server Course for Beginners with 100+ examples - CHECK Constraint

The video tutorial explains the concept of the unique constraint in SQL, which ensures that all values in a specific column are different. It highlights the difference between unique and primary key constraints, demonstrating how to create a table with a unique constraint. The tutorial includes examples of inserting records while maintaining uniqueness and handling errors when attempting to insert duplicate entries. The video concludes with a summary of the unique constraint's purpose and application in SQL.

What is the primary purpose of a unique constraint in SQL?

• To ensure all values in a column are the same

• To restrict the number of columns in a table

• To allow duplicate values in a column

• To ensure all values in a column are different

How many primary key constraints can a table have?

• As many as needed

• Two

• One

• None

What is the first step in creating a table with a unique constraint?

• Add a primary key

• Insert records into the table

• Enter the database using the use command

• Delete existing tables

What happens when you try to insert a duplicate value into a column with a unique constraint?

• The database crashes

• The table is deleted

• The duplicate value is inserted

• An error is shown

What error message is displayed when a duplicate key is inserted into a unique column?

• Unique constraint violation

• Duplicate entry error

• Foreign key constraint error

• Primary key error