How to deal with the "missing right parenthesis " in Oracle 19c? - sql

Question

I have written a piece of code in Oracle database 19c to extract the salary of employees who earns more than the average salary of their respective departments but the query shows "missing right parenthesis". Can anybody help me with it, like where and what the error is all about?
select ename
from emp
where sal > (select round(avg(sal)) as avg_sal, deptno
from emp
group by deptno
order by 2);

Answer 1

You can use these queries to get job done.
select ename
from emp e1
where sal > (select round(avg(sal)) as avg_sal
from emp e2
where e2.deptno = e1.deptno
);
or
select e1.ename
from emp e1,
(
select round(avg(sal)) as avg_sal, deptno
from emp
group by deptno
) e2
where e1.deptno = e2.deptno
and e1.sal > avg_sal
;

Answer 2

Now the output of your subquery is 2 columns and multiple rows, which is against the business logic you described.
To gain the desired result you need to modify the query a bit:
remove the second column in subquery;
remove GROUP BY and ORDER BY clauses from the subquery.
Should be as follows:
SELECT ename FROM emp WHERE sal > (SELECT round(AVG(sal)) AS avg_sal FROM emp);
Now subquery returns only one values which is valuated with each salary in the main query and returns employees' names of ones, that have salary more that average.

Answer 3

The "missing right parenthesis" error is that the ORDER BY clause is not allowed in the sub-query so the SQL parser expects the query to end after the GROUP BY clause.
Once you fix that you get a further error that the sub-query will return multiple rows:
select ename
from emp
where sal > (select round(avg(sal)) as avg_sal, deptno
from emp
group by deptno);
Outputs a different error message:
ORA-00913: too many values
To fix that you need to restrict the sub-query to a single row and correlate the outer-query to the sub-query:
select ename
from emp e
where sal > (select round(avg(sal)) as avg_sal
from emp a
WHERE e.deptno = a.deptno);
Which, for the sample data:
CREATE TABLE emp (ename, sal, deptno) AS
SELECT 'Alice', 100, 1 FROM DUAL UNION ALL
SELECT 'Beryl', 200, 1 FROM DUAL UNION ALL
SELECT 'Carol', 300, 1 FROM DUAL UNION ALL
SELECT 'Debra', 100, 2 FROM DUAL UNION ALL
SELECT 'Ester', 200, 2 FROM DUAL;
Outputs:
ENAME
Carol
Ester
If you want to do it in a single table-scan then you can use analytic functions:
SELECT ename
FROM (
SELECT ename,
sal,
ROUND(AVG(sal) OVER (PARTITION BY deptno)) AS avg_sal
FROM emp
)
WHERE sal > avg_sal;
db<>fiddle here