I have a table where we have staff_id and manager_id. Attached screenshot.
I found managers by using this query:
select e.first_name as employee , m.first_name as manager
from sales.staffs E
inner JOIN sales.staffs M ON M.staff_id = E.manager_id
How do I pull a list of employees who are not managers?
My sample table
You can do it using:
select * from sales.staff
where staff_id not in (select manager_id from sales.staff)
use not exists
select t1.* from from sales.staff t1
where not exists ( select 1 from sales.staff t2 where t1.staff_id=t2.manager_id )
if you use not in then do null chechk
select t.* from sales.staff t
where t.staff_id not in (select manager_id from sales.staff where manager_id IS NOT NULL)
I guess all the ids of managers are stored in the column manager_id.
Also if the column manager_id is null then this employee is also a manager(?).
So to get all the managers you should do:
select * from sales.staffs
where
manager_id is null
or
staff_id in (select distinct manager_id from sales.staffs)
Now to get the employees that are not managers you just negate the condition:
select * from sales.staffs
where
manager_id is not null
and
staff_id not in (select distinct manager_id from sales.staffs)
As an extension on #The Impalers correct answer, your query would become:
select e.first_name as employee , m.first_name as manager
from sales.staffs E
inner JOIN sales.staffs M ON M.staff_id = E.manager_id
WHERE m.manager_id IS NULL
Since you want to have a list of people who are not managers you could go for this solution, which will check if the manager_id is equal to NULL (assuming this means no manager).
A different solution would be to LEFT JOIN based on NOT EXIST, this would filter your table and would significantly lower your fetch time.
Related
There are two tables, employee and dept:
How can I join the two tables and select the department with the least number of employees?
It would have been better to answer if you provided the table structure.
But give this a try:
SELECT deptname
FROM dept
WHERE deptid = (SELECT distinct deptid
FROM employee
ORDER BY COUNT(dept) limit 1);
Please try the following...
SELECT deptid,
deptname,
employeeCount
FROM
(
SELECT dept.deptid AS deptid,
dept.deptname,
COUNT( dept.deptid ) AS employeeCount
FROM dept
JOIN employee ON dept.deptid = employee.deptid
GROUP BY dept.deptid,
dept.deptname
)
GROUP BY deptid
HAVING employeeCount = MIN( employeeCount );
This statement starts with the inner query joining dept to employee on the shared field deptid. It then groups the resulting rows by department and returns to the outer query the department's id and name along with a count of employees for that department.
The outer query groups the data by department again, then selects the details of the department(s) having a count of employees equal to the minimum count of employees.
If you have any questions or comments, then please feel free to post a Comment accordingly.
I'm only answering because MIN isn't needed and LIMIT isn't Oracle:
select d.*
from (select deptid, count(*) as cnt
from employees e
group by deptid
order by count(*) asc
) d
where rownum = 1;
In Oracle 12C+, you don't need the subquery:
select deptid, count(*) as cnt
from employees e
group by deptid
order by count(*) asc
fetch first 1 row only;
Hi :) so my answer is a bit ugly, and full of nested queries. but I tested it and it worked for me...
-- First I created a couple of test tables and added a few records
drop table dept;
drop table employee;
create table dept (deptid number primary key, deptname varchar(20));
create table employee(employee_id number primary key, names varchar(20),
deptid number,foreign key (deptid) references dept(deptid));
insert into dept values(1,'HR');
insert into dept values(2,'Finance');
insert into dept values(3,'IT');
insert into employee values(1,'Tina',1);
insert into employee values(2,'Rob',1);
insert into employee values(3,'Lisa',1);
insert into employee values(4,'Will',2);
insert into employee values(5,'Lina',2);
insert into employee values(6,'Ethel',2);
insert into employee values(7,'Trevor',1);
insert into employee values(8,'Alanea',1);
insert into employee values(9,'Matthew',1);
insert into employee values(10,'Maddie',3);
insert into employee values(11,'Anna',1);
-- According to the added records, the answer we are looking for should be
the department name IT
-- select the department name from department table
select d.deptname from dept d,
/* This is where it gets ugly - basically, it counts the number of
employees in each department, then finds the id of the department that had
the smallest count */
(select deptid from
(select count(deptid) as counter, deptid from employee group by deptid)
where counter =( select min(counter)from
(select count(deptid) as counter, deptid from employee group by deptid))) minid
-- join the tables using deptid
where d.deptid = minid.deptid;
This query gave the correct answer for me even when I changed the records to make finance the correct answer.
If you have any questions give me a yell through the comments :)
select department_name, count(employee_id)
from department d
inner join employee e
on d.employee_id = e.employee_id
having count(employee_id) =
(
select min(count(employee_id)) /*This query returns minimum count*/
from department d
inner join employee e
on d.employee_id = e.employee_id
group by department_name
)
group by department_name;
WITH temp
AS
(SELECT e1.department_id, count(e1.employee_id) emp_count
FROM hr.employees e1
GROUP BY e1.department_id)
SELECT d1.department_name, t1.emp_count employee_count
FROM temp t1
,hr.departments d1
WHERE t1.department_id = d1.department_id(+)
AND NOT EXISTS
(SELECT 1
FROM temp t2
WHERE t2.emp_count < t1.emp_count)
ORDER BY 2,1 ;
I wondering is what I am doing right.
select distinct
Departments.Department_No, Departments.Department_Name
from
Departments
join
Employees on Departments.Department_No = Employees.Department_No
join
Jobs on Jobs.Job_ID = Employees.Job_ID
where
Departments.Department_No not in (select distinct Department_No
from Employees
where Employees.Job_ID like '%SA_REP%');
You want to display distinct values of Department Number and Department Name
You join Employees table with Department on Department Number
You join Jobs table with Employees on Job ID
You filter the result by excluding those Department Numbers of the entire Employee table that have a Job ID matching the pattern %SA_REP%
In my opinion you don't need
the join with the Jobs table
the join with the Employees table
you could maybe see if one of the other users' suggestions can bring performance improvement
SELECT DISTINCT departments.department_no,
departments.department_name
FROM departments
WHERE departments.department_no NOT IN (SELECT DISTINCT department_no
FROM employees
WHERE employees.job_id LIKE '%SA_REP%'
);
You could simply do this using NOT EXISTS instead of using a NOT IN subquery:
SELECT DISTINCT
d.Department_No
,d.Department_Name
FROM Departments d
JOIN Employees e ON d.Department_No = e.Department_No
WHERE NOT EXISTS
(select 1
from Employees e1
where e1.Job_ID like '%SA_REP%'
AND e1.Department_No = e.Department_No);
You can translate where condition without "in".
And you don't need to fetch date from "Jobs" - you don't use it
Select distinct Departments.Department_No, Departments.Department_Name
from Departments
Join Employees on Departments.Department_No = Employees.Department_No
where Employees.Job_ID not like '%SA_REP%';
I am trying to use a sub query on an inner join to get back all department numbers and names from a table that do not have programmer in the department, but I am having a little trouble as it returns no values. Here is my code, thanks for any help.
select Departments.Department_Name, Departments.Department_No
from employees inner join departments
on departments.department_No = employees.Department_No
where Employees.Department_No !=
(select Department_Name
from Employees, Departments
where Job_ID = '%pro%')
From what I can gather, you want something like this:
select d.Department_Name, d.Department_No
from departments d
WHERE NOT EXISTS (SELECT 1 FROM Employees
WHERE d.Department_No = Department_No
AND Job_ID LIKE '%pro%')
This selects all departments, for which there doesn't exist an employee whose job_ib contains 'pro'.
Try this one:
select d1.Department_Name,d1.Department_No
from departments d1
where d1.Department_No in ( select e1.Department_No
from Employees e1
where e1.Department_No=d1.Department_No and
e1.job_id not in ('programmer'));
How do I add a subquery as a column in my SQL script?
e.g.
Select emp_no, name,gender ,
(select department_name from departments where employees.emp_no = departments.emp_no)
from employees
PS: I'm using oracle 8
Going by the semantics, what I understand is that you want an employee's department name to be shown alongside his/her other information. I would suggest you do a join instead:
Select emp_no, name, gender, department_name
from employees emp, departments dept
where emp.emp_no = dept.emp_no;
That looks reasonably sound, I would suggest some (possible typos) cleaning up: add a comma after "gender" and declare the table names, also set the subquery alias
Select employees.emp_no, employees.name, employees.gender,
(select departments.department_name from departments where employees.emp_no = departments.emp_no) as dept_name
from employees
Alternatively, a nice join would would work too, if the other data is feasible:
Select employees.emp_no, employees.name, employees.gender, departments.department_name
from employees
inner join departments on employees.emp_no = departments.emp_no
left join is the best-practice, and should be faster in performance:
Select e.emp_no, e.name, e.gender , d.department_name
from employees e left join departments d on e.emp_no = d.emp_no;
You seem to be missing comma after gender.
Select emp_no, name,gender ,
(select department_name from departments where employees.emp_no = departments.emp_no) as dept_name from employees
The below is what you need. Just added a comma after gender. This subquery would need to return only one row for each result as well or else an error will be seen.
Select emp_no, name,gender,
(select department_name from departments where employees.emp_no = departments.emp_no)
from employees
This query is your answer but it will work only if there is one column mentioned in that if we use more than one column than it will retrun an error .
"Select employee_id,first_name,
(select department_name,manager_id from departments where employees.department_id = departments.department_id) as new_column
from employees;"
can you try this:
SELECT em.emp_no, em."name",em.gender ,
(SELECTdistinctdp.department_name
FROM departments dp
WHERE em.emp_no = dp.emp_no) my_sub
FROM employees em
When using the SQL MIN() function, along with GROUP BY, will any additional columns (not the MIN column, or one of the GROUP BY columns) match the data in the matching MIN row?
For example, given a table with department names, employee names, and salary:
SELECT MIN(e.salary), e.* FROM employee e GROUP BY department
Obviously I'll get two good columns, the minimum salary and the department. Will the employee name (and any other employee fields) be from the same row? Namely the row with the MIN(salary)?
I know there could very possibly be two employees with the same (and lowest) salary, but all I'm concerned with (now) is getting all the information on the (or a single) cheapest employee.
Would this select the cheapest salesman?
SELECT min(salary), e.* FROM employee e WHERE department = 'sales'
Essentially, can I be sure that the data returned along with the MIN() function will matches the (or a single) record with that minimum value?
If the database matters, I'm working with MySql.
If you wanted to get the "cheapest" employee in each department you would have two choices off the top of my head:
SELECT
E.* -- Don't actually use *, list out all of your columns
FROM
Employees E
INNER JOIN
(
SELECT
department,
MIN(salary) AS min_salary
FROM
Employees
GROUP BY
department
) AS SQ ON
SQ.department = E.department AND
SQ.min_salary = E.salary
Or you can use:
SELECT
E.*
FROM
Employees E1
LEFT OUTER JOIN Employees E2 ON
E2.department = E1.department AND
E2.salary < E1.salary
WHERE
E2.employee_id IS NULL -- You can use any NOT NULL column here
The second statement works by effectively saying, show me all employees where you can't find another employee in the same department with a lower salary.
In both cases, if two or more employees have equal salaries that are the minimum you will get them both (all).
SELECT e.*
FROM employee e
WHERE e.id =
(
SELECT id
FROM employee ei
WHERE ei.department = 'sales'
ORDER BY
e.salary
LIMIT 1
)
To get values for each department, use:
SELECT e.*
FROM department d
LEFT JOIN
employee e
ON e.id =
(
SELECT id
FROM employee ei
WHERE ei.department = d.id
ORDER BY
e.salary
LIMIT 1
)
To get values only for those departments that have employees, use:
SELECT e.*
FROM (
SELECT DISTINCT eo.department
FROM employee eo
) d
JOIN
employee e
ON e.id =
(
SELECT id
FROM employee ei
WHERE ei.department = d.department
ORDER BY
e.salary
LIMIT 1
)
Of course, having an index on (department, salary) will greatly improve all three queries.
The fastest solution:
SET #dep := '';
SELECT * FROM (
SELECT * FROM `employee` ORDER BY `department`, `salary`
) AS t WHERE IF ( #dep = t.`department`, FALSE, ( #dep := t.`department` ) OR TRUE );
Another approach can be using Analytical functions. Here is the query using analytical and ROW_NUM functions
select first_name, salary from (select first_name,salary, Row_NUMBER() over (PARTITION BY DEPARTMENT_ID ORDER BY salary ASC) as row_count from employees) where row_count=1;