How do I display the project name with the second highest number of employees?
Relation schema, with primary key and foreign key as applicable:
Employee(Eid,Ename,Address,city,Doj,salary) Project(Pid,Location,Pname,Mng,Client,Branch)
Works(Eid,Pid)
Eid and Pid in Works are ForeignKey.
eid and pid are primary keys in employee and project respectively
select count (*) , pname
from project natural join work
group by pname;
But this will only give the count of employees according to the project... Not the maximum number of employees
select max as ex1
from (Select count(*) as ex1
from works
where PID in ( select distinct pid from works);
I am trying this in linux - oracle
OK,I think the SQL below would return what you want(The number 2 project's name and employee numbers):
select * from
(
select
p.pname,
count(1) as cc
from
work w
join
project p on w.pid = p.pid
join
employee e on w.eid = e.eid
group by
p.pname
order by cc desc limit 2
) tmp order by cc asc limit 1
SELECT COUNT(W.Eid) AS TotalEmployees, P.pname
FROM Works W
INNER JOIN Project P ON W.Pid = P.Pid
GROUP BY P.Pid
ORDER BY TotalEmployees desc
OFFSET 1 ROWS FETCH NEXT 1 ROWS ONLY
Related
I have 4 tables in my db: incoming letters, outgoing letters, local letters and employee. In "letters" tables, there is a register_employee that have register this letter.
Every employee has his/her unique id (for example "3de9a23e-b927-4a27-a66a-c1f30b8c1464").
Tables look like this:
employee:
id first_name last_name age
incoming:
id register_employee summary letter adress date_sent
"Outgoing" and "local" tables look same as "incoming" table.
I need to count how many letters have been registered by each employee and which type.
Example results:
employee incoming outgoing local
Bob Marley 45 33 5
John Travolta 31 10 9
George Bush 98 15 38
I tried to use full joins and nested Select statments, but results that I have got are probably wrong cause I am getting millions of count for each employee (I don't have so many letters in db).
You can use OUTER JOIN and GROUP BY as follows:
-- Updated
You can use multiple sub-query:
select e.id, e.firstname,
(select count(*) from incoming i where i.register_employee = e.id) as incoming_letter,
(select count(*) from outgoing o where o.register_employee = e.id) as outgoing_letter,
(select count(*) from local l where l.register_employee = e.id) as local_letter
from employee e
We count the number of letters under different categories & left join them to the master employee table
select employee.first_name , t1.incoming, t2.outgoing, t3.local from (
select * from employee
left join
(select register_employee, count(*) as incoming from incoming_letters group by register_employee) t1 on employee.id = t1.register_employee
left join
(select register_employee, count(*) as outgoing from outgoing_letters group by register_employee) t2 on employee.id = t2.register_employee
left join
(select register_employee, count(*) as local from local group by register_employee) t3 on employee.id = t3.register_employee ) v
SELECT incom.id,incom.name,incom.incoming,out.outgoings,loc.local
FROM (SELECT
employees.id as id,
employees.short_name as name,
COUNT(incomings.register_employee) as incoming
FROM employees
LEFT JOIN incomings ON incomings.register_employee = employees.id)
GROUP BY employees.id, employees.short_name) as incom
LEFT JOIN (SELECT
employees.id as id,
COUNT(outgoings.register_employee) as outgoings
FROM employees
LEFT JOIN outgoings ON outgoings.register_employee = employees.id
GROUP BY employees.id) as out
ON incom.id=out.id
LEFT JOIN (SELECT
employees.id as id,
COUNT(local.register_employee) as local
FROM employees
LEFT JOIN outgoings ON local.register_employee = employees.id
GROUP BY employees.id) as loc
ON incom.id=loc.id;
What I need:
I am looking for a solution that can give me all the Employee Id's that have the same EmailAddress Column (the filter needs to be by EmailAddress).
I want to know what are the Id's correspondent to the duplicated Email Addresses and retrieve that information.
Table Employee:
Id | PlNumber | EmailAddress | EmployeeBeginingDate | EmployedEndDate | Name UserId(FK) | CreatedBy | CreatedOn
SELECT a.Id,a.EmailAddress
FROM Employee a
INNER JOIN (SELECT
Employee.Id as EmployeeId,
Employee.EmailAddress as EmailAddress,
FROM Employee
GROUP BY Employee.Id,Employee.EmailAddress
HAVING count(Employee.EmailAddress) > 1
) b
ON a.Id= b.EmployeeId
ORDER BY a.Id
I am always getting an error:
the multi-part identifier could not be bound.
I know why the error is happening but I couldn't solve this.
UPDATE: After a few changes the query is returning 0 rows but I know it should return at least 3 rows that I have duplicate values.
Try the below query as you have an aliased table Employee as a. So in place of Employee, you have to use a.
SELECT a.Id, a.EmailAddress
FROM Employee a
INNER JOIN (SELECT
Employee.EmailAddress as EmailAddress
FROM Employee
GROUP BY Employee.EmailAddress
HAVING count(Employee.EmailAddress) > 1
) b
ON a.EmailAddress = b.EmailAddress
ORDER BY a.Id
Live db<>fiddle demo.
Assuming the ids are different on each row, I would go for exists:
SELECT e.Id, e.EmailAddress
FROM Employee e
WHERE EXISTS (SELECT 1
FROM Employee e2
WHERE e2.EmailAddress = e.EmailAddress AND
e2.Id <> e.Id
)
ORDER BY e.EmailAddress;
Or, if you want to know the number of matches, use window functions:
SELECT e.Id, e.EmailAddress, cnt
FROM (SELECT e.*, COUNT(*) OVER (PARTITION BY e.EmailAddress) as cnt
FROM Employee e
) e
WHERE cnt >= 2;
I want to get the number of employees by department and I wrote this script using Oracle but it always says that there is a missing expression
The columns used in my tables :
department :name (the name of the department) -
depnum (the id of the department"primary key"),
employee : empnum (the id of the employee) -
depnum (the id of the department in which the employee in question is working "foreign key")
Query:
select
s.name
from
department s
inner join
employee p on s.depnum = p.depnum
group by
s.name
having
count(p.empnum) = max(select count(p.empnum)
from employee p, department s
where s.depnum = p.depnum
group by s.name) ;
If you want the number of employees by department, I would expect something like this:
select s.name, count(*) as num_employees
from department s inner join
employe p
on s.depnum = p.depnum
group by s.name ;
If you want the department names with the maximum number of names, you can use a having clause:
select s.name, count(*) as num_employees
from department s inner join
employe p
on s.depnum = p.depnum
group by s.name
having count(*) = (select max(cnt)
from (select count(*) as cnt
from employee e2
group by e2.depnum
) e2
);
The problem with your query is that you are attempting to take the max() of a subquery. That syntax is not allowed -- and not necessary.
you sql statement is not correct that's why it thrown that error. I think you tried something like below
select s.name
from department s
inner join employe p on s.depnum=p.depnum
group by s.name
having count(p.empnum)=
select max(cnt) from
(
select count(p.empnum) as cnt
from employe p join department s
on s.depnum=p.depnum
group by s.name
) t;
I am having trouble writing a query that will select all Skills, joining the Employee and Competency records, but only return one skill per employee, their newest Skill. Using this sample dataset
Skills
======
id employee_id competency_id created
1 1 1 Jan 1
2 2 2 Jan 1
3 1 2 Jan 3
Employees
===========
id first_name last_name
1 Mike Jones
2 Steve Smith
Competencies
============
id title
1 Problem Solving
2 Compassion
I would like to retrieve the following data
Skill.id Skill.employee_id Skill.competency_id Skill.created Employee.id Employee.first_name Employee.last_name Competency.id Competency.title
2 2 2 Jan 1 2 Steve Smith 2 Compassion
3 1 2 Jan 3 1 Mike Jones 2 Compassion
I was able to select the employee_id and max created using
SELECT MAX(created) as created, employee_id FROM skills GROUP BY employee_id
But when I start to add more fields in the select statement or add in a join I get the 'Column 'xyz' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.' error.
Any help is appreciated and I don't have to use GROUP BY, it's just what I'm familiar with.
The error that you were getting is because SQL Server requires any item in the SELECT list to be included in the GROUP BY if there is an aggregate function being used.
The problem with that is you might have unique values in some columns which can throw off the result. So you will want to rewrite the query to use one of the following:
You can use a subquery to get this result. This gets the max(created) in a subquery and then you use that result to get the correct employee record:
select s.id SkillId,
s.employee_id,
s.competency_id,
s.created,
e.id employee,
e.first_name,
e.last_name,
c.id competency,
c.title
from Employees e
left join Skills s
on e.id = s.employee_id
inner join
(
SELECT MAX(created) as created, employee_id
FROM skills
GROUP BY employee_id
) s1
on s.employee_id = s1.employee_id
and s.created = s1.created
left join Competencies c
on s.competency_id = c.id
See SQL Fiddle with Demo
Or another way to do this is to use row_number():
select *
from
(
select s.id SkillId,
s.employee_id,
s.competency_id,
s.created,
e.id employee,
e.first_name,
e.last_name,
c.id competency,
c.title,
row_number() over(partition by s.employee_id
order by s.created desc) rn
from Employees e
left join Skills s
on e.id = s.employee_id
left join Competencies c
on s.competency_id = c.id
) src
where rn = 1
See SQL Fiddle with Demo
For every non-aggregated column you add to your SELECT statement you need to update your GROUP BY to include it.
This article may help you understand why.
;WITH
MAX_SKILL_created AS
(
SELECT
MAX(skills.created) as created,
skills.employee_id
FROM
skills
GROUP BY
skills.employee_id
),
MAX_SKILL_id AS
(
SELECT
MAX(skills.id) as id,
skills.employee_id
FROM
skills
INNER JOIN MAX_SKILL_created
ON MAX_SKILL_created.employee_id = skills.employee_id
AND MAX_SKILL_created.created = skills.created
GROUP BY
skills.employee_id
)
SELECT
* -- type all your columns here
FROM
employees
INNER JOIN MAX_SKILL_id
ON MAX_SKILL_id.employee_id = employees.employee_id
INNER JOIN skills
ON skills.id = MAX_SKILL_id.id
INNER JOIN competencies
ON competencies.id = skills.competency_id
If you are using SQL Server than you can use OUTER APPLY
SELECT *
FROM employees E
OUTER APPLY (
SELECT TOP 1 *
FROM skills
WHERE employee_id = E.id
ORDER BY created DESC
) S
INNER JOIN competencies C
ON C.id = S.competency_id
I want to show the names of all employees from the EMPLOYEES table who are working on more than three projects from the PROJECT table.
PROJECTS.PersonID is a a foreign key referencing EMPLOYEES.ID:
SELECT NAME, ID
FROM EMPLOYEES
WHERE ID IN
(
SELECT PersonID, COUNT(*)
FROM PROJECTS
GROUP BY PersonID
HAVING COUNT(*) > 3
)
Can I have both PersonID, COUNT(*) in that subquery, or there must be only one column?
Not in an IN clause (or at least not the way you are trying to use it. Some RDBMSs allow tuples with more than one column in the IN clause but it wouldn't help your case here)
You just need to remove the COUNT(*) from the SELECT list to achieve your desired result.
SELECT NAME, ID
FROM EMPLOYEES
WHERE ID IN
(
SELECT PersonID
FROM PROJECTS
GROUP BY PersonID
HAVING COUNT(*) > 3
)
If you wanted to also return the count you could join onto a derived table or common table expression with more than one column though.
SELECT E.NAME,
E.ID,
P.Cnt
FROM EMPLOYEES E
JOIN (SELECT PersonID,
Count(*) AS Cnt
FROM PROJECTS
GROUP BY PersonID
HAVING Count(*) > 3) P
ON E.ID = P.PersonID
To answer your question, you can only have 1 column for the IN subquery. You could get your results using the query below:
SELECT e.ID
,e.Name
FROM dbo.Projects p
LEFT OUTER JOIN dbo.Employees e
ON p.PersonID = e.ID
GROUP BY e.ID
,e.Name
HAVING COUNT(*) > 3