What is the Linq Query of the following SQL - sql

Question

I am new to nHibernate. I have following SQL inner join query,
SELECT e.name,
d.deptname
FROM demo_employee AS e
INNER JOIN demo_department AS d
ON e.departmentid = d.deptid
What is the linq expression using Query Over of the following sql query.
I have written the following query but it is qiving me error at following place "c.Department.DeptId".
var Query =
Session.QueryOver<Employee>()
.JoinQueryOver<Department>(c => c.Department.DeptId)
.Where(k => k.Name == k.DeptId);

Answer 1

Here is the QueryOver version.
We are using aliasing, ie: Declaration of the null reference Employee employee = null to be used for fully-typed access to all properties. NHibernate Expression parser will convert them into strings (column names) later based on mapping.
Also we could get references to FROM parts of the QueryOver. The query represents Employee, and the joined query represents the Department (depQuery), which we can directly filter.
Finally we can use List() to get (SELECT) all mapped properties, or do some projection: .Select() or .SelectList(). With projection, we should be working with some DTO.
// aliasing, see the Projections of the SELECT clause
Employee employee = null;
Department department = null;
// the Employee query, with alias
var query = session.QueryOver<Employee>(() => employee);
// this way we can have reference to department query, if needed
var depQuery = query.JoinQueryOver<Department>(() => employee.Department, () => department);
// WHERE
// filtering the Employee
query.Where(e => e.Name == "Undefined");
// the department filtering
depQuery.Where(d => d.DeptName == "Management");
// paging, if needed
query.Skip(100);
query.Take(10);
1) select all properties
var list = query.List<Employee>();
var employeeName = list.ElementAt(0).Name;
var departmentName = list.ElementAt(0).Department.DeptName;
2) projection
// The DTO class to be projected into
public class MyDTO
{
public virtual string EmployeeName { get; set; }
public virtual string DepartmentName { get; set; }
}
// Select with projection of just two columns
MyDTO dto = null;
// SELECT
// projection, explicit property/column to be selected only
query.SelectList(l => l
// the full power of aliasing
.Select(() => employee.Name).WithAlias(() => dto.EmployeeName)
.Select(() => department.DeptName).WithAlias(() => dto.DepartmentName)
);
var list = query
.TransformUsing(Transformers.AliasToBean<MyDTO>())
.List<MyDTO>();