Not able to get exact latest records with two columns having same value - in SQL Server - sql

Question

I am trying to get distinct records for a specific department from the table employee.
I have tried with this code in SQL Server, and I'm getting this error:
Error: employeeId is invalid in the select list because it is not contained in either aggregate function or the GROUP BY clause.
My code:
SELECT
name, department, MAX(jointime) LatestDate, employeeId
FROM
employee
WHERE
department = 'Mechanical'
GROUP BY
name
Records in DB:
name department joinTime EmployeeId
-----------------------------------------------------------
Erik Mechanical 2019-07-06 11:59:59 456
Tom Mechanical 2019-07-06 11:59:59 789
Erik Computer 2019-07-05 11:59:59 222
Erik Computer 2019-07-04 11:59:59 111
Erik Mechanical 2019-07-01 11:59:59 123
I want to achieve the result when a query for 'Mechanical' is executed. The latest record should be fetched from DB for a particular department.
name department joinTime EmployeeId
-----------------------------------------------------------
Erik Mechanical 2019-07-06 11:59:59 456
Tom Mechanical 2019-07-06 11:59:59 789

Answer 1

Assuming the key is [Name] and not [EmployeeId]
One option is the WITH TIES clause, and thus no need for aggregation
Example
Select Top 1 with ties *
From employee
Where department='Mechanical'
Order By Row_Number() over (Partition By [Name] order by joinTime Desc)
Returns
name department joinTime EmployeeId
Erik Mechanical 2019-07-06 11:59:59.000 456
Tom Mechanical 2019-07-06 11:59:59.000 789

Answer 2

You can use EXISTS:
SELECT e.*
FROM employee e
WHERE e.department='Mechanical'
AND NOT EXISTS (
SELECT 1 FROM employee
WHERE department = e.department
AND name = e.name AND joinTime > e.joinTime
)
See the demo.
Results:
> name | department | joinTime | EmployeeId
> :--- | :--------- | :------------------ | ---------:
> Erik | Mechanical | 2019-07-06 11:59:59 | 456
> Tom | Mechanical | 2019-07-06 11:59:59 | 789

Answer 3

You can use ROW_NUMBER to mark the latest row for each employee, or CROSS APPLY to run a correlated subquery for each employee.
with q as
(
SELECT name, department, jointime, employeeId,
row_number() over (partition by name, order by joinTime desc) rn
FROM employee where department='Mechanical'
)
select name, department, jointime, employeeId
from q
where rn = 1
or
with emp as
(
select distinct name from employee
)
select e.*
from q
cross apply
(
select top 1 *
from employee e2
where e2.name = q.name
order by joinDate desc
) e

Answer 4

Just add department,employeeId to the GROUP BY
SELECT name , department, MAX(jointime) LatestDate , employeeId
FROM employee where department='Mechanical'
GROUP BY name, department, employeeId

Answer 5

You need to use AGGREGATE Functions for fields which are used in SELECT statement:
SELECT name,
MIN(department)
, MAX(jointime) LatestDate,
, MIN(employeeId)
FROM employee where department='Mechanical'
GROUP BY name
SQL server finds all records with names Tom or Erik, but SQL Server does not know what one value from multiple rows should be chosen for the fields such as department or employeeId. By using aggregrate functions, you are advising SQL Server to get the MIN, MAX, SUM, COUNT values of that columns.
OR use those columns to the GROUP BY clause to get all unique rows:
SELECT name
, department
, jointime
, employeeId
FROM employee where department='Mechanical'
GROUP BY name
, department
, jointime
, employeeId