Getting Hierarchical data

1) Hierarchical Query using a Recursive CTE

The basic syntax structure for a CTE is shown below:

WITH MyCTE AS 

(SELECT EmpID, FirstName, LastName,ManagerID 

FROM Employee

WHERE ManagerID IS NULL )

SELECT *FROM MyCTE



Building a Recursive CTE

  WITH MyCTE AS 
  ( 
    SELECT EmpID, FirstName, LastName, ManagerID FROM Employee
   WHERE ManagerID IS NULL 
   UNION ALL

    SELECT EmpID, FirstName, LastName, ManagerID FROM Employee

    INNER JOIN MyCTE ON Employee.ManagerID = MyCTE.EmpID WHERE Employee.ManagerID IS NOT NULL 

)
SELECT *FROM MyCTE


Using C#.Net



IList<Employee> GetEmployees(Employee manager)
{
    var result = new List<Employee>();

    var employees = _employeeDb.Employees
                               .Where(e => e.ManagerEmployeeNumber == manager.EmployeeNumber)
                               .ToList();

    foreach (var employee in employees)
    {
        result.Add(employee);
        result.AddRange(GetEmployees(employee));
    }

    return result;
}

2) What is SOLID?

SOLID are five basic principles whichhelp to create good software architecture. SOLID is an acronym where:-

• S stands for SRP (Single responsibility principle
• O stands for OCP (Open closed principle)
• L stands for LSP (Liskov substitution principle)
• I stands for ISP ( Interface segregation principle)
• D stands for DIP ( Dependency inversion principle)

• S stands for SRP (Single responsibility principle):- A class should take care of only one responsibility.
• O stands for OCP (Open closed principle):- Extension should be preferred over modification.
• L stands for LSP (Liskov substitution principle):- A parent class object should be able to refer child objects seamlessly during runtime polymorphism.
• I stands for ISP (Interface segregation principle):- Client should not be forced to use a interface if it does not need it.
• D stands for DIP (Dependency inversion principle) :- High level modules should not depend on low level modules but should depend on abstraction.

2) 

HTTP	HTTPS
URL begins with “http://”	URL begins with “https://”
It uses port 80 for communication	It uses port 443 for communication
Unsecured	Secured
Operates at Application Layer	Operates at Transport Layer
No encryption	Encryption is present
No certificates required	Certificates require