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Interview Questions and answers - SQL Server Day 3

Question:  What is difference between Function and Stored Procedure in SQL Server?

Answer: Some basic difference between stored procedure and function is described below.

The main difference between stored procedure and function is Function must returns a value while stored procedure can or not this is optional. Function can have input parameter only while stored procedure can have both input/output parameters. Function can be called from stored procedures but stored procedures can’t call from function. 

Function 
Stored Procedure
Function must returns a value
In stored procedure it is optional 
Function can have input parameter only
Stored procedure can have both input and output parameter s
Function can be called from procedure
Procedure can‘t be called from function
Function allows only select statement
Procedure allows DML statement(SELECT, INSERT, UPDATE, DELETE)
Function can use in SQL statement like WHERE/HAVING/SELECT
Procedure can’t be use in SQL statement like WHERE/HAVING/SELECT
Function can return table and can be treated as another row set. This can be use in joins with other tables.
Transaction can’t be implement
Transaction can be implement in stored procedure

Question: What is subquery in SQL server?

Answer: A SELECT statement query nested in another t-SQL  statement is called subquery. SELECT subquery always run independently and return result set to t-SQL statement. Subquery doesn't depend on statement in which it is nested.

Question: What are different types of joins in SQL Server?

Answer: Types of joins in SQL Server is given bellow.
1- Cross join
2- Inner join
3- Outer join
    a)Left Outer join
    b)Right Outer join
    c)Full Outer join
4- Self join

Question: What is Cross Join in SQL Server?

Answer: Joins between tables without conditions produces the Cartesian  product called cross join. The size of Cartesian product result set is the number of rows in the first table multiplied by the number of rows in the second table.

example:


SELECT p.bID, t.Name AS Territory
FROM Sales.SalesPerson p
CROSS JOIN Sales.SalesTerritory t
ORDER BY p.BID;


Question: What is inner join in SQL Server?

Answer: Inner join display only the rows of tables which matched in both joined table on a particular column. This is the default type of join in the query.

Question: What is Outer join and it type in SQL Server?

Answer: Outer join includes related and rows and also not related rows. there are three type of outer joins in SQL Server.
a) Left Outer Join: the Left Outer join display all the rows of first table and all matched rows of second table but not appears unmatched rows of second table.
b) Right Outer join: Right Outer joined display all the row of second table and matched rows of first table but not appears unmatched rows if first table.
c) Full Outer Join: Full Outer join display all the rows of joined tables whether they matched or not.

Question: What is Self join in SQL Server?


Answer: Join between a table and it's alias is called self join. In this join table join itself but same name may create confusion so we used alias of table as second table.

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Syntax:

{ $add: [ <expression1>, <expression2>, ... ] }

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Example: Suppose we have a Test collection as below.

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Query to add 2 days in CreatedDate

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