I have two table in Access, Employee and Dept.
In Employee table there is empname column and deptcode column, while in Dept table there is deptcode column and deptname column.
I want to do a query which shows empname, deptcode and deptname in a new table. I have tried:
SELECT empname, deptcode, deptname
FROM employee,dept
And it cannot work as the deptcode exist in both table and it creates error. Can anyone kindly tell me how to solve this error problem?
You need to alias your tables in the FROM clause and then use the table alias in the SELECT statement.
select e.empname,d.deptcode,d.deptname
from employee e
inner join dept d
on e.deptcode = d.deptcode;
You just need to associate the columns with the tables in the form of aliases or table name itself. Something like this should work.
select employee.empname,
dept.deptcode,
dept.deptname from employee,dept
where employee.deptcode = dept.deptcode;
Note that I have added a condition to match the department code for the employees
Related
Tables
Need to update department table's dcount column based on number of employees working in each department from employee table's dno column.
Tried using
update department set dcount=(select count() from employee INNER JOIN department ON employee.dno=department.dnumber group by dno);*
which gave an error : more than one row returned by a subquery used as an expression
Desired result is:
**dname|dnumber|dcount
Research|5|4
Admin|4|3
Headquarters|1|1**
Need help please.
Thanks in advance.
Gruheeth
Your subquery (select count() ...) returns several rows, one per employee, where postgres expect only one row from this subquery in order to update one row at a time in the department table. In this case, you case use a cte instead :
WITH list AS
(
select dno, count(*) AS dno_count
from employee
group by dno
)
update department AS d
set dcount = l. dno_count
from list AS l
where d.dnumber = l.dno ;
I have a employee hive table with columns name and department. where 1 employee can belongs to multiple departments.
name, department
xxx,finance
xxx,hr
xxx,transport
xxx,sale
yyy,finance
yyy,hr
yyy,transport
zzz,finace
zzz,hr
zzz,transport
zzz,sale
I need to know distinct employee name who does not belongs to "sale" department.
As of hive 0.13
Select name from employee
where employee.name not in
(select name from employee where department = 'sale')
group by name;
Hopefully names are unique across employees.
You could write a subquery to pull all names that are in sales. Then join that query's results back to your table.
select
results.name,
results.department
from
(select e.name
from employee e
where e.department='sale' group by e.name) invalid_names
right join
(select
e.name,
e.department
from employee e) results
on invalid_names.name = results.name
where invalid_names.name is null;
I'd imagine there is a better way to do this, but this should work :)
When I write this query in sql plus show me error (ORA-00998: must name this expression with a column alias)
create or replace view vw_salary as select dname ,
(select count(*) from employee where dno=department.dnumber) from department;
Columns in a view need to have a name. So, you need as after the subquery:
create or replace view vw_salary as
select dname,
(select count(*) from employee e where e.dno = d.dnumber
) as NumEmployees
from department d;
I strongly encourage you to use table aliases and qualified column names (that is use the table alias). This is particularly important for correlated subqueries, where it is easy to make a mistake and that is hard to debug.
I also note that the view is called vw_salary, but there is no salary information.
select department.dname, count(employee.dno) as empCount
from department
left join employee
on employee.dno = department.dnumber
group by department.dname
I think this will be more efficient than your current format
It means you need to name the count expression ... try the following, you can change "TheCount" to any name you want to use.
create or replace view vw_salary as select dname ,
(select count(*) AS TheCount from employee where dno=department.dnumber) from department;
imagine I have two tables, the "departments" table and the "employee" table.
This employee table has a column for "category".
I'd like to make a query for selecting departments that only have a specified type of employees.
Thank you.
You will need to perform a join from your departments and employee table on whatever columns link these two tables together. In the where clause, you will specify what types of employees that you want.
This will return a row for each employee, which might not be what you want. You may use the distinct function on the important columns that you're looking for in the departments table to get the final answer.
select distinct dept_id
from employee
where category = 'cat1'
and dept_id not in (select distinct dept_id
from employee
where dept_id <> 'cat1');
SELECT dept_id
FROM departments
WHERE dept_id NOT IN
(SELECT DISTINCT dept_id
FROM employee
WHERE category_id != #specified_category)
This query assumes there are no departments with no employees, since it will also return those empty departments. If that's a problem, you can add:
AND dept_id IN (SELECT distinct dept_id FROM employee)
Select d.id_department from departments d where not exists
(Select e.id_employee from employees e where e.category!=your_category and e.id_department=d.id_department) you also need to verify that department has employees.
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