/*-- Query 1:

--Write a SQL query to fetch all the duplicate records from a table.
--Tables Structure:

create table users
(
user_id int primary key,
user_name varchar(30) not null,
email varchar(50));

insert into users values
(1, 'Sumit', 'sumit@gmail.com'),
(2, 'Reshma', 'reshma@gmail.com'),
(3, 'Farhana', 'farhana@gmail.com'),
(4, 'Robin', 'robin@gmail.com'),
(5, 'Robin', 'robin@gmail.com');

/*select user_id, user_name, email
from(
select *, row_number() over (partition by user_name, email) as row_num
from users)x
where x.row_num>1*/

/*select * from users
where rowid not in
(select min(rowid)
from users
group by user_name, email)*/


-- Query 2:

--Write a SQL query to fetch the second last record from a employee table.

--Tables Structure:


/*create table employee
( emp_ID int primary key
, emp_NAME varchar(50) not null
, DEPT_NAME varchar(50)
, SALARY int);

insert into employee values(101, 'Mohan', 'Admin', 4000);
insert into employee values(102, 'Rajkumar', 'HR', 3000);
insert into employee values(103, 'Akbar', 'IT', 4000);
insert into employee values(104, 'Dorvin', 'Finance', 6500);
insert into employee values(105, 'Rohit', 'HR', 3000);
insert into employee values(106, 'Rajesh',  'Finance', 5000);
insert into employee values(107, 'Preet', 'HR', 7000);
insert into employee values(108, 'Maryam', 'Admin', 4000);
insert into employee values(109, 'Sanjay', 'IT', 6500);
insert into employee values(110, 'Vasudha', 'IT', 7000);
insert into employee values(111, 'Melinda', 'IT', 8000);
insert into employee values(112, 'Komal', 'IT', 10000);
insert into employee values(113, 'Gautham', 'Admin', 2000);
insert into employee values(114, 'Manisha', 'HR', 3000);
insert into employee values(115, 'Chandni', 'IT', 4500);
insert into employee values(116, 'Satya', 'Finance', 6500);
insert into employee values(117, 'Adarsh', 'HR', 3500);
insert into employee values(118, 'Tejaswi', 'Finance', 5500);
insert into employee values(119, 'Cory', 'HR', 8000);
insert into employee values(120, 'Monica', 'Admin', 5000);
insert into employee values(121, 'Rosalin', 'IT', 6000);
insert into employee values(122, 'Ibrahim', 'IT', 8000);
insert into employee values(123, 'Vikram', 'IT', 8000);
insert into employee values(124, 'Dheeraj', 'IT', 11000);

select * from 
(select *, row_number() over(Order by emp_ID desc) as row_num
from employee)
where row_num = 2*/

-- Query 3:

--Write a SQL query to display only the details of employees who either earn the highest salary
--or the lowest salary in each department from the employee table.

--Tables Structure:


create table employee
( emp_ID int primary key
, emp_NAME varchar(50) not null
, DEPT_NAME varchar(50)
, SALARY int);

insert into employee values(101, 'Mohan', 'Admin', 4000);
insert into employee values(102, 'Rajkumar', 'HR', 3000);
insert into employee values(103, 'Akbar', 'IT', 4000);
insert into employee values(104, 'Dorvin', 'Finance', 6500);
insert into employee values(105, 'Rohit', 'HR', 3000);
insert into employee values(106, 'Rajesh',  'Finance', 5000);
insert into employee values(107, 'Preet', 'HR', 7000);
insert into employee values(108, 'Maryam', 'Admin', 4000);
insert into employee values(109, 'Sanjay', 'IT', 6500);
insert into employee values(110, 'Vasudha', 'IT', 7000);
insert into employee values(111, 'Melinda', 'IT', 8000);
insert into employee values(112, 'Komal', 'IT', 10000);
insert into employee values(113, 'Gautham', 'Admin', 2000);
insert into employee values(114, 'Manisha', 'HR', 3000);
insert into employee values(115, 'Chandni', 'IT', 4500);
insert into employee values(116, 'Satya', 'Finance', 6500);
insert into employee values(117, 'Adarsh', 'HR', 3500);
insert into employee values(118, 'Tejaswi', 'Finance', 5500);
insert into employee values(119, 'Cory', 'HR', 8000);
insert into employee values(120, 'Monica', 'Admin', 5000);
insert into employee values(121, 'Rosalin', 'IT', 6000);
insert into employee values(122, 'Ibrahim', 'IT', 8000);
insert into employee values(123, 'Vikram', 'IT', 8000);
insert into employee values(124, 'Dheeraj', 'IT', 11000);

Select * from(
Select *, first_value(SALARY) over (partition by DEPT_NAME order by SALARY desc) as max_salary,
last_value(salary) over (partition by DEPT_NAME order by SALARY desc
range between unbounded preceding and unbounded following) as min_salary
from employee)
where SALARY =max_salary or SALARY = min_salary