I am trying to get a list of all the employee names and their managers and I cannot figure out how to do it. I have attached the relational model.
In DEPT we know the department number (dept_nbr) which is attached to EMPLOYEE through emp_dept and we know the department manager (dept_mgr) which is attached to EMPLOYEE through emp_nbr
select
mgr.emp_nbr ManagerID,
emp.emp_nbr EmployeeID,
emp.emp_lname, emp.emp_fname,
mgr.emp_lname as mgr_lname, mgr.emp_fname as mgr_fname
from
dept
inner join employee as mgr on dept.dept_mgr = mgr.emp_nbr
inner join employee as emp on dept.dept_nbr = emp.emp_dept
Related
I have the following relational schema.
EMPLOYEE(Fname, Lname, Ssn, Salary, Dno)
DEPARTMENT(Dname, Dnumber, Mgr_ssn)
For each department, I would like to retrieve the department number, manager first name and the departments average salary.
Below is my attempt. I get the department number and average salary but I can't understand how to retrieve the department manager name without filtering rows which would change the value of the average salary.
SELECT D.Dnumber, AVG(E.Salary)
FROM EMPLOYEE E JOIN DEPARTMENT D ON E.Dno = D.Dnumber
GROUP BY D.Dnumber
How do I retrieve the manager first name within this query?
Presumably, the link to the manager is through the SSN. To me, it is a bad idea to use PII (personally identifiable information) for such a purpose.
In any case, you need two joins to get the first name, so you are half-way there:
select d.dnumber, avg(e.salary), em.fname
from employee e join
department d
on e.dno = d.dnumber left join
employee em
on e.ssn = em.mgr_ssn
group by d.dnumber, em.fname;
I'm trying to figure out a query which shows the names of the employees who worked in more than 2 departments along with their wage and contact details. I have two tables employees and department. Both of these having the EmployeeName field. I know we have to use the Count function but don't really know how to create the query.
here the tablename and Fields:
Employee (employeeName, wage, contactNo)
Department (employeeName, departmentNo, hours, startDate)
You SQL query would be the following
SELECT e.employeeName, count(departmentNo) FROM Employee e
INNER JOIN Department d ON e.employeeName=d.employeeName
GROUP BY e.employeeName
HAVING COUNT(departmentNo)>2
you can use following query:
SELECT e.employeeName, count(d.departmentname)
FROM Employee e, Department d
where e.deptid=d.deptid
GROUP BY e.employeeName
HAVING COUNT(e.deptid)>=2
so I'm stuck on this question where it says:
write a query to retrieve a list of ALL departments in alphabetical order containing the columns DEPARTMENT_ID , DEPARTMENT_NAME , LAST_NAME , FIRST_NAME where last_name and first_name are the name of the Manager of the Department wherever there is one.
I'm have the HR database using the departments, employees table what i have written so far is:
select department_id, department_name, e.last_name, e.first_name
from departments d, employees e
where e.department_id=d.department_id
and d.department_id=e.department_id
and d.manager_id=e.manager_id
having department_name = '%Manager%';
yet i can't figure it out, any tips will help thanks!
A having clause relates to a group by. Where you have no group by, there is no meaning for a having clause.
You just need your join to get the record in the employees table for the manager.
select department_id, department_name, e.last_name, e.first_name
from departments d, employees e
where d.manager_id=e.id
Better is to use the newer join syntax,
select dept.department_id, dept.department_name, emp.last_name, emp.first_name
from departments dept
inner join employees emp on dept.manager_id = emp.id
You don't need conditions for e.department_id=d.department_id and d.department_id=e.department_id, (for one thing these are redundant, so you would only need one if they were needed) because the employees.department_id field refers to the department the employee is in, and what you want is the manager employee record for the department. The manager employee record for the department is represented as the foreign key to the primary key of the employee table.
this might help you...
`select e.first_name,e.last_name,d.department_id ,d.department_name from employees e,departmets d where d.manager_id=e.employee_id order by d.department_name;`
I am trying to write a query that lists the name of a manager and the number of people they manage.
In the Manager table we have the managers name and id.
In the Employee table we have the employees name, id and managerID.
I don't understand how to get the count of the employees that a manager manages.
SELECT COUNT(e.EmpID), m.ManagerID
FROM Employee e
INNER JOIN Manager m
ON e.ManagerID= m.ManagerID
GROUP BY m.ManagerID
SELECT m.Name, COUNT(e.id) AS NumberOfEmployeesManaged
FROM Manager m INNER JOIN Employee e ON m.id = e.managerID
GROUP BY m.Name
That should do it I think, just a simple count of the employee ids after joining the manager and employee tables, grouped on manager name.
SELECT count(emp.empid), mgr.managerid
FROM Employee emp
INNER JOIN Manager mgr ON emp.managerid=mgr.managerid
GROUP BY mgr.managerid;
I don't know if you can use the COUNT aggregator in a JOIN. But you can run 2 queries. One would select the manager's name & id. The 2nd would look like this:
$id = the manager's id
SELECT COUNT(*) FROM Employee WHERE managerID=$id
Alternately, you could not use COUNT and run a query like this:
SELECT id FROM Employee WHERE managerID=$id
Then the # of resulting rows would be the count of employees managed by the manager.
So I have a table that has, employee number, employee name, supervisor number.
I want to run a query that will retrieve employee name, employee number, supervisor name and supervisor number. Only one employee doesn't have a supervisor meaning it will have to display nulls. How would I do this? I'm using Oracle SQL Plus. My attempts haven't worked at all! Any help would be much appreciated.
SELECT ename Employee, empno Emp#, super Manager#
FROM emp;
That gets me three of the columns but to be honest I don't even know where to start to get the supervisors names.
It's for university, but I'm studying for a test it's not for an assignment so no cheating happening here :).
The following should work, and give you nulls if the employee has no supervisor:
SELECT empGrunt.ename Employee
, empGrunt.empno EmpNum
, empSuper.ename SupervisorName
, empSuper.empno SupervisorName
FROM emp empGrunt LEFT OUTER JOIN emp empSuper
ON empGrunt.super = empSuper.empno
Assuming that SupervisorNumber is a foreign key relationship back to the Employee table (where it's the EmployeeNumber of the supervisor's record), then you need to use an outer join.
What you need in this case is a left join:
select
e.EmployeeName,
e.EmployeeNumber,
s.EmployeeName as SupervisorName
from Employee e
left join Employee s on s.EmployeeNumber = e.SupervisorNumber