Row_number() and group by together not working - sql

Question

I wrote below query, I need to know what am I doing wrong. After adding row_number(), the output is always this error:
ORA-00979: not a GROUP BY expression
00979. 00000 - "not a GROUP BY expression"
*Cause:
*Action:
Error at Line: 22 Column: 32
The SQL Developer tool tip suggested to append row_number() in group by together with Is_Data_Picked. But as I know row_number() is an analytical function to count the each row, and it can't be use in GROUP BY clause
When I use row_number() inside GROUP BY, then it shows the below error
ORA-30484: missing window specification for this function
30484. 00000 - "missing window specification for this function"
*Cause: All window functions should be followed by window specification, like () OVER ()
*Action:
Error at Line: 26 Column: 26
I want to use both "GROUP BY" and "ROW_NUMBER()" in my query.
Kindly help me to rectify this issue and suggest me the solution.
Query:
SELECT *
FROM
(SELECT
COUNT(DISTINCT Emp_Code) totalEmployees,
SUM(CASE WHEN pay_code = 999 THEN AMOUNT ELSE '0' END) net_salary,
SUM(CASE WHEN pay_code = 997 THEN AMOUNT ELSE '0' END) gross_earning,
SUM(CASE WHEN pay_code = 998 THEN AMOUNT ELSE '0' END) gross_deduction,
Is_Data_Picked,
ROW_NUMBER() OVER (ORDER BY (Emp_Code)) AS ROW_NUM
FROM
Xxmpcd_Salary_Detail_Table
WHERE
Prayas_Erp_Org_Id LIKE '302-%'
AND Yyyymm = '201805'
GROUP BY
Is_Data_Picked, ROW_NUMBER()) mytbl
WHERE
ROW_NUM < 600 AND ROW_NUM > 0

Answer 1

This is the relevant part of your subquery:
SELECT . . .
ROW_NUMBER() OVER (ORDER BY (Emp_Code)) AS ROW_NUM
FROM Xxmpcd_Salary_Detail_Table
WHERE Prayas_Erp_Org_Id LIKE '302-%' AND Yyyymm = '201805'
GROUP BY Is_Data_Picked, ROW_NUMBER()
You have an error in the first ROW_NUMBER() because Emp_Code is not in the GROUP BY. You have an error in the second because ROW_NUMBER() is not a function.
I could speculate that you intend:
SELECT . . .
ROW_NUMBER() OVER (ORDER BY Emp_Code) AS ROW_NUM
FROM Xxmpcd_Salary_Detail_Table
WHERE Prayas_Erp_Org_Id LIKE '302-%' AND Yyyymm = '201805'
GROUP BY Is_Data_Picked, Emp_Code
If you don't want to aggregate by Emp_Code, then you might intend:
SELECT . . .
ROW_NUMBER() OVER (ORDER BY MIN(Emp_Code)) AS ROW_NUM
FROM Xxmpcd_Salary_Detail_Table
WHERE Prayas_Erp_Org_Id LIKE '302-%' AND Yyyymm = '201805'
GROUP BY Is_Data_Picked