I'm trying to write a Ado SQL statement for my Access table and I'm getting the wrong results.
Employee Table
ID Name DriverID
1 Alex 1
2 Tom 2
3 Trevor 3
4 PHIL 0
5 Gina 4
Vehicle Table
ID PLATE EMPLOYEEID INSERVICE
1 123XYZ 1 N
2 456GFR 2 Y
3 TFV4FG 3 Y
4 F6GK7D 4 Y
5 GEY7GH 1 Y
I want result of All employes and to display the Vehcicle info if they are assigned to it.
Result should be
Name Plate
Alex GEY7GH
Tom 456GFR
Trevor TFV4FG
PHIL
Gina F6GK7D
SELECT Employee.ID, Employee.FirstName, Vehicles.Plate, Vehicles.InService
FROM Employee LEFT JOIN Vehicles ON Employee.ID = Vehicles.DriverID
WHERE (((Vehicles.InService)=True));
Does not display PHIL who is not assigned to a vehicle.
Just add the condition inside the join, making sure to use parentheses to avoid problems when joining with constants or anything but simple equals:
SELECT Employee.ID, Employee.FirstName, Vehicles.Plate, Vehicles.InService
FROM Employee LEFT JOIN Vehicles ON (Employee.ID = Vehicles.DriverID AND Vehicles.InService = True)
From the above tables, it looks like the DriverID Column in employee table aligns with the EmployeeID column in the vehicles table and the issue is the on clause in the join.
SELECT
Employee.ID
,Employee.FirstName
,Vehicles.Plate
,Vehicles.InService
FROM
Employee
LEFT JOIN Vehicles ON Employee.DRIVERID = Vehicles.EMPLOYEEID
WHERE
(((Vehicles.InService)=True));
Well, in a normal database, you would move the WHERE condition to the ON clause. But I don't think that MS Access supports this:
SELECT e.ID, e.FirstName, v.Plate, v.InService
FROM Employee as e LEFT JOIN
Vehicles as v
ON e.ID = v.DriverID AND v.InService = True;
An alternative is a subquery:
SELECT e.ID, e.FirstName, v.Plate, v.InService
FROM Employee as e LEFT JOIN
(SELECT v.*
FROM Vehicles as v
WHERE v.InService = True
) as v
ON e.ID = v.DriverID ;
Related
SELECT E.DNO as DeptNum, COUNT(E.SSN) as EmployeeCount, COUNT(D.ESSN) as DependentCount
FROM Dependent D
RIGHT OUTER JOIN Employee E ON D.ESSN = E.SSN
GROUP BY E.DNO
The goal is to find the total number of employees and total number of dependents for every department. I am utilizing an Employee Table that features Employee, SSN, Department Number and a Dependent Table that has Dependent SSN, Birthdate, and Gender.
The output should be as follows
Dept Num Employee Count DependentCount
1 1 0
2 3 7
3 5 2
But, instead I am getting
Dept Num Employee Count DependentCount
1 1 0
2 9 7
3 4 2
One thing of note is the dependent's SSN is equivalent to the parent's SSN - that is the only way to define the relationship between the tables. Also, I know I need an outer join because we want to list ALL departments, despite the fact there are 0 mentions of it for Dept 1 in Dependent Table.
Can anyone tell me why this isn't working?
Try using distinct so things don't get double counted:
SELECT E.DNO as DeptNum, COUNT(DISTINCT E.SSN) as EmployeeCount,
COUNT(DISTINCT D.ESSN) as DependentCount
FROM Employee E LEFT JOIN
Dependent D
ON D.ESSN = E.SSN
GROUP BY E.DNO
I have two tables, one that flags a user as having passed a course, and a list of courses per job code. I'm trying to query to return a record for all users that are missing classes.
Here are the tables:
Attended
--------
empid jobcode classcode grade
555 1 100 A
555 1 101 A
444 2 200 A
JobClassCode
--------
jobcode classcode
1 100
1 101
1 102
2 100
2 200
3 300
3 301
I started with this query to find classes with a missing user:
select * from attended at
right outer join jobcodeclass jc on at.jobcode = jc.jobcode and at.classcode = jc.classcode
I then tried to take that to build a correlated subquery, but I don't see a way to return both the user ID and missing course ID:
select * from jobcodeclass oq where classcode in (select jc.classcode from attended at
right outer join jobcodeclass jc on at.jobcode = jc.jobcode
and at.classcode = jc.classcode and jc.jobcode = oq.jobcode
and oq.classcode = jc.classcode and empid is null)
Generate all the possible classes that each employee needs by joining on the jobcode. The see which ones the student attended:
select ej.empid, ej.jobcode, jss.classcode
from (select distinct empid, jobcode from attended) ej join
JobClassCode jcc
on jcc.jobcode = ej.jobcode left join
attended a
on a.empid= e.empid and a.jobcode = ej.jobcode and
a.classcode = jcc.classcode
where a.empid is null;
If you just need the employees, use select distinct ej.empid.
I have two tables one is teacher and another is Department which is mentioned below.
Teacher Table
Id Name
1 xyz
2. Gjd
3. Dftr
4 dhdk
Department Table
Id Name EMPID
1 SQL. 2
2. PHP. 4
3. JAVA. 1
4 PEARL. 5
QUESTION
i want those records of teacher which are not link with any Department.
you can use following statement using left join then filter Teacher that not matched
SELECT t.*
FROM Teacher t
left join Department d on d.EMPID = t.Id
where d.id is null
SELECT * FROM teachers WHERE
id NOT IN (SELECT DISTINCT EMPID FROM departments) ;
Hope this helps.!!
you can do it by inner query..
select * from teacher where id not in (select empid from department);
I am trying to convert the following query:
select *
from employees
where emp_id not in (select distinct emp_id from managers);
into a form where I represent the subquery as a join. I tried doing:
select *
from employees a, (select distinct emp_id from managers) b
where a.emp_id!=b.emp_id;
I also tried:
select *
from employees a, (select distinct emp_id from managers) b
where a.emp_id not in b.emp_id;
But it does not give the same result. I have tried the 'INNER JOIN' syntax as well, but to no avail. I have become frustrated with this seemingly simple problem. Any help would be appreciated.
Assume employee Data set of
Emp_ID
1
2
3
4
5
6
7
Assume Manger data set of
Emp_ID
1
2
3
4
5
8
9
select *
from employees
where emp_id not in (select distinct emp_id from managers);
The above isn't joining tables so no Cartesian product is generated... you just have 7 records you're looking at...
The above would result in 6 and 7 Why? only 6 and 7 from Employee Data isn't in the managers table. 8,9 in managers is ignored as you're only returning data from employee.
select *
from employees a, (select distinct emp_id from managers) b
where a.emp_id!=b.emp_id;
The above didnt' work because a Cartesian product is generated... All of Employee to all of Manager (assuming 7 records in each table 7*7=49)
so instead of just evaluating the employee data like you were in the first query. Now you also evaluate all managers to all employees
so Select * results in
1,1
1,2
1,3
1,4
1,5
1,8
1,9
2,1
2,2...
Less the where clause matches...
so 7*7-7 or 42. and while this may be the answer to the life universe and everything in it, it's not what you wanted.
I also tried:
select *
from employees a, (select distinct emp_id from managers) b
where a.emp_id not in b.emp_id;
Again a Cartesian... All of Employee to ALL OF Managers
So this is why a left join works
SELECT e.*
FROM employees e
LEFT OUTER JOIN managers m
on e.emp_id = m.emp_id
WHERE m.emp_id is null
This says join on ID first... so don't generate a Cartesian but actually join on a value to limit the results. but since it's a LEFT join return EVERYTHING from the LEFT table (employee) and only those that match from manager.
so in our example would be returned as e.emp_Di = m.Emp_ID
1,1
2,2
3,3
4,4
5,5
6,NULL
7,NULL
now the where clause so
6,Null
7,NULL are retained...
older ansii SQL standards for left joins would have been *= in the where clause...
select *
from employees a, managers b
where a.emp_id *= b.emp_id --I never remember if the * is the LEFT so it may be =*
and b.emp_ID is null;
But I find this notation harder to read as the join can get mixed in with the other limiting criteria...
Try this:
select e.*
from employees e
left join managers m on e.emp_id = m.emp_id
where m.emp_id is null
This will join the two tables. Then we discard all rows where we found a matching manager and are left with employees who aren't managers.
Your best bet would probably be a left join:
select
e.*
from employees e
left join managers m on e.emp_id = m.emp_id
where
m.emp_id is null;
The idea here is you're saying that you want to select everything from employees, including anything that matches in the manager table based on emp_id and then filtering out the rows that actually have something in the manager table.
Use Left Outer Join instead
select e.*
from employees e
left outer join managers m
on e.emp_id = m.emp_id
where m.emp_id is null
left outer join will preserve the rows from m table even if they do not have a match i e table based on the emp_id field. The we filter on where m.emp_id is null - give me all the rows from e where there's no matching record in m table.
A bit more on the subject can be found here:
Visual representation of joins
from employees a, (select distinct emp_id from managers) b implies cross join - all posible combinations between tables (and you needed left outer join instead)
The MINUS keyword should do the trick:
SELECT e.* FROM employees e
MINUS
Select m.* FROM managers m
Hope that helps...
select *
from employees
where Not (emp_id in (select distinct emp_id from managers));
I have two Tables "Employees" and "EmployeesCompanies", Employees contains a list of all employees, and employeescompanies contains a list of all companies associated with an employee:
Table 1 (Employees)
EmployeeID
1
2
3
Table 2 (EmployeesCompanies)
EmployeeID
1
2
I want to return
3 which is the missing record from EmployeesCompanies, here is the linq code I'm using:
var queryOrphanedEmployees = (from a in db.Employees
join b in db.EmployeesCompanies
on a.EmployeeID equals b.EmployeeID
into outer
from c in outer.DefaultIfEmpty()
select new { a.EmployeeID}).ToList();
However this returns:
1
2
Which is exactly opposite to what I want.
You should be able to do something like this if you've set up the foreign keys properly
from e in Employees
where !e.EmployeesCompanies.Any()
select e