Group by function

[Kido]

I want to do a report which is from different tables and I want to use the group by function e.g

select a.staff_num, sum(a.amount), b.first_name, b.last_name, c.staff_num
where ........
group by a.staff_num;

When I try to execute, I get an error message not a group by function. What could be the problem or is it that grout by function is for a single table?

 

[pgaec]

Can you copy and paste the exact error message?

I assume that you got something like "Column 'b.first_name' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause." Is that right?

 

[Kido]

This is the script:

SELECT "EMPLOYEES"."FIRST_NAME",
"EMPLOYEES"."MIDDLE_NAME",
"EMPLOYEES"."LAST_NAME",
"EMPLOYEES"."JOB_CATEGORY",
"EMPLOYEES"."AREA",
"INVOICE_LINES"."STAFF_NUM",
"INVOICE_LINES"."AMOUNT",
"INVOICE_LINES"."LINE_TYPE",
"INVOICE_LINES"."INV_CODE"
FROM "EMPLOYEES",
"INVOICE_LINES"
WHERE ( "EMPLOYEES"."AREA" = 2060) AND
( "EMPLOYEES"."JOB_CATEGORY" NOT IN ('40') )
GROUP BY INVOICE_LINES.STAFF_NUM;

and this is the exact error:

ORA-00979: not a GROUP BY expression