Alternative to GROUP BY to consolidate repeating values in single column - sql

Question

I'm using DB2 which apparently doesn't let you use the GROUP BY clause when it's returning more than one column. I have records that have repeating values for ID and name, for example:
EmpID | - name - | code
___________________________________
111111 | Williams | 1
---------------------------------
111111 | Williams | 2
----------------------------------
111112 | Davis | 3
---------------------------------
111113 | Gomez | 1
----------------------------------
111113 | Gomez | 3
----------------------------------
(Excuse my formatting) I need to get a single instance of each employee with a code (doesn't matter which code instance gets omitted as long as one shows up per employee).
Normally I could do:
SELECT * FROM employees GROUP BY EmpID;
DB2 doesn't let you do this for some reason. It says " The grouping is inconsistent." You can do:
SELECT EmpID from employees GROUP BY EmpID;
but if you introduce more return values then it gives you the error.
I tried looking into using a subquery and derived tables but I'm not sure how to compose it to select only one code value and exclude the records with a repeating employee value. If anyone has an answer or could point me to another thread that addresses this problem I would appreciate it very much.

Answer 1

It is required in most databases to GROUP BY each column in the SELECT list that is not in an aggregate function that is why you received an error message.
For your situation if it does not matter what code value is returned, then you can use an aggregate function and group by:
SELECT EmpID, name, MIN(code) code
FROM employees
GROUP BY EmpID, name;
See Demo
The group by is applied to both the EmpId and name, while the aggregate function is applied to the code column.
Note that due to that EmpID and name are functionally dependent on each other (as far as we can see from the sample you posted and the "repeating values" comment), the following two queries will return the same, identical results as the above query:
--- GROUP BY EmpID
------------------
SELECT EmpID, MIN(name) name, MIN(code) code
FROM employees
GROUP BY EmpID;
--- GROUP BY name
-----------------
SELECT MIN(EmpID) EmpID, name, MIN(code) code
FROM employees
GROUP BY name;