Interview Questions and answers - SQL Server Day 2

Question: What is an index in SQL Server?

Answer: Index is responsible for arranging data physically to speed up query performance. An index is a physical structure containing the pointers of the data. We can create index one or more columns of the table. Creating a relational index on the table is called the row-store index. It is either a clustered or non-clustered index. There are two types of indexes.

1-  Clustered index
2-  Non-clustered index
3-  A new index introduced in SQL Server 2014. “Columnstore index.”

Question: What is a cursor in SQL Server?

Answer: Curser is responsible for manipulating data in a set on a row by row basis. Actually, curser is the database object used by the application.

Question: Types of an index in SQL Server.

Answer: Types of the index is given below.
  1. Clustered index
  2. Non-clustered index
  3. Columnstore index 
Question: What are the constraints in SQL Server?

Answer: Constraints are the rules enforced on data columns on the table. This ensures the accuracy and reliability of the data in the database. Constraints define some conditions that restrict the column to remain true while inserting or updating or deleting data in the column.

Question: Types of constraints in SQL Server?

Answer: Types of constraints is given below.
  1. NOT NULL- This constraint is responsible for a column to confirm that a column cannot have a null value.
  2. DEFAULT – This constraint provides a default value when specified none for this column.
  3. UNIQUE- This constraint ensures that each row for the column has a different value.
  4. PRIMARY KEY- The primary key constraint is a combination of a NOT NULL constraint and a UNIQUE constraint. This constraint ensures that the specific column for a table has a unique identity.
  5. FOREIGN KEY- This constraint responsible for uniquely identified rows/records in any other database table.
  6. CHECK- The CHECK responsible for enables a condition to check the value being entered into a record 

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