I need to retrieve the name of those departments in which no students are enrolled.
Table: department
dept_id dept_name
1 IT
2 Electrical
3 Civil
4 Mechanical
5 Chemical
Table: stud_member
f_name dept_id age
AB 2 19
Rose 3 22
May 1 20
Noor 1 21
Haya 1 19
April 3 23
Sakina 2 20
For example the names of mechanical and chemical. I have written this query for it using outer join (explicitly maybe?) But is shows an error.
please tell me that why i cannot write:
SELECT dept_id, dept_name
FROM department
LEFT JOIN stud_member ON (WHERE NOT department.dept_id = stud_member.dept_id);
I will be grateful if anyone will tell me the correct answer!
Assuming dept_id in stud_member can not be NULL which is true when dept_id is a FOREIGN KEY
SELECT dept_id, dept_name
FROM department
WHERE dept_id NOT IN (SELECT dept_id FROM stud_member);
as suggested using NOT EXISTS does not have this problem
SELECT d.dept_id, d.dept_name
FROM department d
WHERE NOT EXISTS (SELECT * FROM stud_member s WHERE d.dept_id = s.dept_id);
You can select all departments where Right part of Left JOIN is NULL
SELECT d.dept_id, d.dept_name
FROM department d
LEFT JOIN stud_member sm ON d.dept_id = sm.dept_id
WHERE sm.dept_id IS NULL
Related
Here are the details of the tables:
Employee :
emp_ID | Primary Key
emp_name | Varchar
emp_email | varchar <br>
emp_dept_id | Foreign Key
Departments :
dept_ID | Primary Key
dept_name | Varchar
emp_id | Foreign Key
Manager details are already there in the employee table.
I am using Oracle Database.
Employee:
emp_ID emp_name emp_email emp_dept_id
1 Cyrus abc#xyz.com 10
2 Andrew xyz#abc.com 20
3 Mark xyz#abc.com 10
4 Tony xyz#abc.com 10
5 Elvis xyz#abc.com 20
6 Rock xyz#abc.com 10
7 George xyz#abc.com 20
8 Mary xyz#abc.com 10
9 Thomas xyz#abc.com 20
10 Martin xyz#abc.com 10
Depqartments:
dept_id dept_name emp_id
10 Accounts 4
20 Development 9
These are the data in the tables. In Department table, emp_id(Foreign key) indicates the head/manager of the department .
You can try following query:
SELECT
D.DEPT_ID,
D.DEPT_NAME,
D.EMP_ID AS MANAGER_ID,
E.EMP_NAME AS MANAGER_NAME,
E.EMP_EMAIL AS MANAGER_EMAIL,
E.CNT AS "number of employees"
FROM
DEPARTMENT D
JOIN (
SELECT
EMP_ID,
EMP_NAME,
EMP_EMAIL,
EMP_DEPT_ID,
COUNT(1) OVER(
PARTITION BY EMP_DEPT_ID
) AS CNT
FROM
EMPLOYEE
) E ON ( E.DEPT_ID = D.EMP_DEPT_ID
AND E.EMP_ID = D.EMP_ID );
Cheers!!
This is pretty straightforward. You want to get the department details (1) and also include the employees associated with that department (2).
Get the department details:
SELECT <dept_col1>, <dept_col2>, ...
FROM Department
Get a summary of employees per department:
SELECT dept_ID, <aggregation> AS MyAgg
FROM department
GROUP BY dept_ID
Here you replace <aggregation> with whatever you're trying to find. In your case it would be COUNT(*).
Combine the two results. You want to join the data from (2) to (1). How are these two tables related? Here you write a LEFT JOIN to connect them on the PK/FK relationship:
SELECT
dept.<col1>, dept.<col2>, ...,
COALESCE(emp.MyAgg,0) AS MyAgg
FROM Department dept
LEFT JOIN (
SELECT dept_ID, <aggregation> AS MyAgg
FROM department
GROUP BY dept_ID
) emp ON dept.<FK> = emp.<PK>
Get the department manager's info by adding another LEFT JOIN:
SELECT
dept.<col1>, dept.<col2>, ...,
mgr.<col1>,
COALESCE(emp.MyAgg,0) AS MyAgg -- In case there are 0 employees
FROM Department dept
LEFT JOIN employee mgr ON dept.<FK> = mgr.<PK>
LEFT JOIN (
SELECT dept_ID, <aggregation> AS MyAgg
FROM department
GROUP BY dept_ID
) emp ON dept.<FK> = emp.<PK>
Give it a try and see how far you get. If you get stuck let me know.
I have a database:
Staff Name
1 Blake
2 Jake
Mgr Emp
2 6
2 8
3 5
4 7
Is it possible to search up all employees but list them under the manager?
Select all:
Staff Name Mgr
1 Blake null
2 Jake null
6 Scott 2
8 Jack 2
3 Clark null
5 Martin 3
4 Smith null
7 Scott 4
And is there a way to look up the team when a staff is searched?
Search: "Scott"
Returns:
Staff Name Mgr
2 Jake null
6 Scott 2
8 Jack 2
http://rextester.com/OAREI7219 is solution
CREATE TABLE Managers (
MgrID int ,
EmpID int
)
CREATE TABLE Staff (
EmpID int,
name nvarchar(50)
)
Query is ;
SELECT
s.EmpID AS Staff,
s.name AS Name,
m.MgrID
FROM Staff s LEFT JOIN Managers m ON s.EmpID = m.EmpID ;
GO
Assuming that you have:
a table "staff" with all the people in the company. For clarity I will rename the "Staff" column to "id".
a many to many table "staff_manager" to link employees with their managers. For clarity I will rename the "Mgr" column to "manager_id" and the "Emp" to "employee_id".
all tables named lowercase and plural.
You may do:
SELECT employees.id, employees.name, managers.id, managers.name
FROM staff as employees
LEFT JOIN employee_managers ON (employee_managers.employee_id = employees.id)
LEFT JOIN staff as managers ON (managers.id = employee_managers.manager_id)
for the second query you add a where clause to the above query:
WHERE managers.name = "Scott" OR employees.name = "Scott"
NOTE: If you may change the model of your database, I would suggest to
set a UNIQUE constrain on the employee_id of the staff_managers table,
so that one employee can have ONLY ONE manager.
To get All Employees with their managers. Try
Select staff.Id,Staff.name,managers.mgr
From staff left join managers on staf.id=managers.emp
To search about employee and get his team with the manager also. Try
— Search: 'scott'
Select staff.Id,Staff.name,managers.mgr
From staff left join managers on staf.id=managers.emp
Where managers.mgr =(select t.mgr from managers as t where t.emp='scott')
Union all
Select staff.Id,Staff.name,managers.mgr
From managers left join staff on staf.id=managers.mgr
Where managers.emp='scott'
hi i have problem in sql query example
Employee
empid empname
1 gan
2 sam
Designation
id desig empid
1 sr officerr 1
2 jr officer 1
3 manager 2
i want join tables and want Employee Table repeated records Null
result like
empid name desig id
1 gan sr officerr 1
1 NULL jr officer 2
2 sam manager 3
i working on query but i not getting result
SELECT DISTINCT designatin.empid, employee.empname,designatin.desig
FROM designatin INNER JOIN employee e ON employee.empid = designatin.empid
GROUP BY employee.empid, employee.empname, designatin.desig
can anybody have solution?
Change the inner join to a left join:
SELECT DISTINCT designatin.empid, employee.empname,designatin.desig
FROM designatin LEFT JOIN employee e ON employee.empid = designatin.empid
GROUP BY employee.empid, employee.empname, designatin.desig
Let try this, it will help you
SELECT e.empid, e.empname,d.desig ,d.id
FROM employee e
INNER JOIN Designation d ON e.empid = d.empid
See DEMO
Folks,
All am looking for is to extend the INNER JOIN. Let me just get to the point. I have two tables Dept & Emp. One Dept can have multiple Emp's & not the other way around.
Table Dept
Dept_id Dept_Name
1 IT
2 HR
3 Other
Table Emp
Emp_id Dept_id Emp_Name
11 1 John
12 1 Jill
13 2 Jack
14 3 Jared
15 1 Jim
16 1 Jarret
17 2 Jacob
I need to JOIN it on Dept_id
Expected Results
Dept_id Dept_name Emp_id Emp_Name
1 IT 11 John
NULL NULL 12 Jill
NULL NULL 15 Jim
NULL NULL 16 Jarret
2 HR 13 Jack
NULL NULL 17 Jacob
3 Other 14 Jared
Hope I conveyed what i want precisely. Its just a regular Inner Join on a Foreign Key Constraint. But, I want the values from the First Table (Dept) to be NULL-ed except for the First Match. That being said, I don't care what's the first match. See it below - Just the result for the Dept_id 1.
Expected Results (Only for Dept_id = 1)
It could be
Dept_id Dept_name Emp_id Emp_Name
1 IT 11 John
NULL NULL 12 Jill
NULL NULL 15 Jim
NULL NULL 16 Jarret
OR
Dept_id Dept_name Emp_id Emp_Name
1 IT 15 Jim
NULL NULL 12 Jill
NULL NULL 11 John
NULL NULL 16 Jarret
OR
Two other possibilities.
Thanks in advance. Sorry for the long explanation even though its a simple case.
I agree with Ic. that this is a crazy query that seems to be doing something that your application should be doing instead of your sql query, that being said, it's fun to write those queries :)
SELECT CASE WHEN RowNumber = 1 THEN Dept_id ELSE NULL END AS Dept_id,
CASE WHEN RowNumber = 1 THEN Dept_name ELSE NULL END AS Dept_name,
Emp_id, Emp_Name
FROM Dept d
INNER JOIN
(SELECT ROW_NUMBER() OVER (PARTITION BY Dept_id ORDER BY Emp_Name) AS RowNumber,
Dept_id, Dept_name, Emp_id, Emp_Name
FROM Emp ) t on t.Dept_id = d. Dept_id
select case
when lag(d.dept_id) over (partition by d.dept_id order by e.emp_id) = d.dept_id then null
else d.dept_id
end as dept_id,
case
when lag(d.dept_name) over (partition by d.dept_id order by e.emp_id) = d.dept_name then null
else d.dept_name
end as dept_name,
e.emp_id,
e.emp_name
from dept d
join emp e on e.dept_id = d.dept_id
order by d.dept_id, d.dept_name, e.emp_id
Honestly, I'm not really sure why you want this result. Formatting is usually best left for the UI layer and NOT your database server. Doing it this way makes the data look like the non-first-employees for each department actually do not have a department, and it fundamentally breaks any sorting or editing functions you may have in your client.
However, you could try:
SELECT FormattedDept.Dept_id, FormattedDept.Dept_Name, Emp.Emp_id, Emp.Emp_Name
FROM Emp
LEFT OUTER JOIN
(
SELECT Dept.Dept_id, Dept.Dept_Name, MIN(Emp_id) AS Emp_id
FROM Dept
INNER JOIN Emp ON Dept.Dept_id = Emp.Dept_id
GROUP BY Dept.Dept_id, Dept.Dept_Name
) FormattedDept ON Emp.Dept_id = FormattedDept.Dept_id
AND Emp.Emp_id = FormattedDept.Emp_id
ORDER BY Emp.Dept_id, Emp.Emp_id
SQL Fiddle Demo
As I mention in my comment above, I'm not sure that you would really want the results to return in the way you are asking. Consider this. If the result set was exported to Excel, and a user changed the sort, then you would lose what dept employee 1-x was in and employee 0 would still show their department. I would suggest you group by Dept_id, and not null out the dept_id and dept_name. Handle the display of that data in your display code.
WITH newRecord
AS
(
SELECT "Emp_id", "Dept_id", "Emp_Name",
ROW_NUMBER() OVER (PARTITION BY "Dept_id" ORDER BY "Emp_id" ASC) RN
FROM Emp
)
SELECT CASE WHEN RN = 1 THEN b."Dept_id" ELSE NULL END AS "Dept_ID",
CASE WHEN RN = 1 THEN b."Dept_Name" ELSE NULL END AS "Dept_Name",
"Emp_id", "Emp_Name"
FROM newRecord a
INNER JOIN Dept b ON a."Dept_id" = b."Dept_id"
SQLFiddle Demo
because i cant think of a reason you would want that other then reporting purposes then you can also do this by using SQL*Plus formmating.
just run the following command before the query in SQL*Plus
break on dept_id skip 1
Enjoy.
How would do the following in SQL
"select dept names who have more than 2 employees whose salary is greater than 1000" ?
DeptId DeptName
------ --------
1 one
2 two
3 three
EmpId DeptId Salary
----- ------ ------
121 1 2000
122 1 2000
123 1 5000
124 1 4000
131 2 2000
132 2 6000
133 2 1000
134 2 1000
125 3 1000
126 3 20000
RESULT: one
How about something like this?
SELECT D.DeptName FROM
Department D WHERE (SELECT COUNT(*)
FROM Employee E
WHERE E.DeptID = D.DeptID AND
E.Salary > 1000) > 2
SELECT DEPTNAME
FROM(SELECT D.DEPTNAME,COUNT(EMPID) AS TOTEMP
FROM DEPT AS D,EMPLOYEE AS E
WHERE D.DEPTID=E.DEPTID AND SALARY>1000
GROUP BY D.DEPTID
)
WHERE TOTEMP>2;
select min(DEPARTMENT.DeptName) as deptname
from DEPARTMENT
inner join employee on
DEPARTMENT.DeptId = employee.DeptId
where Salary > 1000
group by (EmpId) having count(EmpId) > =2
hope this helps
select DeptName from DEPARTMENT inner join EMPLOYEE using (DeptId) where Salary>1000 group by DeptName having count(*)>2
select D.DeptName from [Department] D where D.DeptID in
(
select E.DeptId from [Employee] E
where E.Salary > 1000
group by E.DeptId
having count(*) > 2
)
select deptname from dept_1
where exists
(
SELECT DeptId,COUNT(*)
FROM emp_1
where salary>1000
and emp_1.deptid=dept_1.deptid
GROUP BY DeptId
having count(*)>2)
1:list name of all employee who earn more than RS.100000 in a year.
2:give the name of employee who earn heads the department where employee with employee I.D
My main advice would be to steer clear of the HAVING clause (see below):
WITH HighEarners AS
( SELECT EmpId, DeptId
FROM EMPLOYEE
WHERE Salary > 1000 ),
DeptmentHighEarnerTallies AS
( SELECT DeptId, COUNT(*) AS HighEarnerTally
FROM HighEarners
GROUP
BY DeptId )
SELECT DeptName
FROM DEPARTMENT NATURAL JOIN DeptmentHighEarnerTallies
WHERE HighEarnerTally > 2;
The very early SQL implementations lacked derived tables and HAVING was a workaround for one of its most obvious drawbacks (how to select on the result of a set function from the SELECT clause). Once derived tables had become a thing, the need for HAVING went away. Sadly, HAVING itself didn't go away (and never will) because nothing is ever removed from standard SQL. There is no need to learn HAVING and I encourage fledgling coders to avoid using this historical hangover.