Rewriting uncorrelated subquery to correlated subquery
0
I am working with a default oracle scott database with additional table PROJECT, where there are two columns: projectno and empno.
I want to select names of employees with the highest salaries for each project.
I know how to do it with uncorrelated subquery:
SELECT p.projno,
e.sal,
e.ename
FROM emp e
INNER
JOIN proj_emp p
ON e.empno = p.empno
WHERE (e.sal, p.projno)
IN (SELECT MAX(e.sal),
p.projno
FROM emp e INNER JOIN proj_emp p
ON e.empno = p.empno
GROUP BY p.projno)
However, i was asked to do it with a correlated subquery written in a WHERE clause, but i am wondering if it is possible?
sql oracle subquery correlated-subquery
asked Nov 12 at 11:35
MartinKitty
257
add a comment |
0
I am working with a default oracle scott database with additional table PROJECT, where there are two columns: projectno and empno.
I want to select names of employees with the highest salaries for each project.
I know how to do it with uncorrelated subquery:
SELECT p.projno,
e.sal,
e.ename
FROM emp e
INNER
JOIN proj_emp p
ON e.empno = p.empno
WHERE (e.sal, p.projno)
IN (SELECT MAX(e.sal),
p.projno
FROM emp e INNER JOIN proj_emp p
ON e.empno = p.empno
GROUP BY p.projno)
However, i was asked to do it with a correlated subquery written in a WHERE clause, but i am wondering if it is possible?
sql oracle subquery correlated-subquery
asked Nov 12 at 11:35
MartinKitty
257
Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in aWHEREcaluse
– MartinKitty
Nov 12 at 11:46
add a comment |
0
0
0
I am working with a default oracle scott database with additional table PROJECT, where there are two columns: projectno and empno.
I want to select names of employees with the highest salaries for each project.
I know how to do it with uncorrelated subquery:
SELECT p.projno,
e.sal,
e.ename
FROM emp e
INNER
JOIN proj_emp p
ON e.empno = p.empno
WHERE (e.sal, p.projno)
IN (SELECT MAX(e.sal),
p.projno
FROM emp e INNER JOIN proj_emp p
ON e.empno = p.empno
GROUP BY p.projno)
However, i was asked to do it with a correlated subquery written in a WHERE clause, but i am wondering if it is possible?
sql oracle subquery correlated-subquery
asked Nov 12 at 11:35
MartinKitty
257
I am working with a default oracle scott database with additional table PROJECT, where there are two columns: projectno and empno.
I want to select names of employees with the highest salaries for each project.
I know how to do it with uncorrelated subquery:
SELECT p.projno,
e.sal,
e.ename
FROM emp e
INNER
JOIN proj_emp p
ON e.empno = p.empno
WHERE (e.sal, p.projno)
IN (SELECT MAX(e.sal),
p.projno
FROM emp e INNER JOIN proj_emp p
ON e.empno = p.empno
GROUP BY p.projno)
However, i was asked to do it with a correlated subquery written in a WHERE clause, but i am wondering if it is possible?
sql oracle subquery correlated-subquery
sql oracle subquery correlated-subquery
asked Nov 12 at 11:35
MartinKitty
257
asked Nov 12 at 11:35
MartinKitty
257
edited Nov 12 at 11:43
asked Nov 12 at 11:35
MartinKitty
257
asked Nov 12 at 11:35
MartinKitty
257
asked Nov 12 at 11:35
MartinKitty
257
257
Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in aWHEREcaluse
– MartinKitty
Nov 12 at 11:46
add a comment |
Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in aWHEREcaluse
– MartinKitty
Nov 12 at 11:46
Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in a
WHERE caluse– MartinKitty
Nov 12 at 11:46
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in a
WHERE caluse– MartinKitty
Nov 12 at 11:46
add a comment |
2 Answers
2
active
oldest
votes
2
I would do :
SELECT t.*
FROM (SELECT p.projno, e.sal, e.ename,
DENSE_RANK() OVER (PARTITION BY p.projno ORDER BY e.sal DESC) AS Seq
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) t
WHERE Seq = 1;
EDIT : If you want to do it with correlated subquery then i would rewrite your query to make correlated :
SELECT p.projno, e.sal, e.ename
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
WHERE e.sal = (SELECT MAX(e1.sal)
FROM emp e1 INNER JOIN
proj_emp p1
ON e1.empno = p1.empno
WHERE p1.projno = p.projno
);
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
I forgot to mention, that in exercise instruction it was said to write correlated subquery inWHEREclause
– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but acorrelated subqueryis required. I useduncorrelated subquery
– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
add a comment |
1
Use window functions:
SELECT projno, sal, ename
FROM (SELECT p.projno, e.sal, e.ename,
MAX(e.sal) OVER (PARTITION BY p.projno) as max_sal
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) ps
WHERE sal = max_sal;
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
2
I would do :
SELECT t.*
FROM (SELECT p.projno, e.sal, e.ename,
DENSE_RANK() OVER (PARTITION BY p.projno ORDER BY e.sal DESC) AS Seq
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) t
WHERE Seq = 1;
EDIT : If you want to do it with correlated subquery then i would rewrite your query to make correlated :
SELECT p.projno, e.sal, e.ename
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
WHERE e.sal = (SELECT MAX(e1.sal)
FROM emp e1 INNER JOIN
proj_emp p1
ON e1.empno = p1.empno
WHERE p1.projno = p.projno
);
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
I forgot to mention, that in exercise instruction it was said to write correlated subquery inWHEREclause
– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but acorrelated subqueryis required. I useduncorrelated subquery
– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
add a comment |
2
I would do :
SELECT t.*
FROM (SELECT p.projno, e.sal, e.ename,
DENSE_RANK() OVER (PARTITION BY p.projno ORDER BY e.sal DESC) AS Seq
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) t
WHERE Seq = 1;
EDIT : If you want to do it with correlated subquery then i would rewrite your query to make correlated :
SELECT p.projno, e.sal, e.ename
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
WHERE e.sal = (SELECT MAX(e1.sal)
FROM emp e1 INNER JOIN
proj_emp p1
ON e1.empno = p1.empno
WHERE p1.projno = p.projno
);
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
I forgot to mention, that in exercise instruction it was said to write correlated subquery inWHEREclause
– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but acorrelated subqueryis required. I useduncorrelated subquery
– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
add a comment |
2
2
2
I would do :
SELECT t.*
FROM (SELECT p.projno, e.sal, e.ename,
DENSE_RANK() OVER (PARTITION BY p.projno ORDER BY e.sal DESC) AS Seq
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) t
WHERE Seq = 1;
EDIT : If you want to do it with correlated subquery then i would rewrite your query to make correlated :
SELECT p.projno, e.sal, e.ename
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
WHERE e.sal = (SELECT MAX(e1.sal)
FROM emp e1 INNER JOIN
proj_emp p1
ON e1.empno = p1.empno
WHERE p1.projno = p.projno
);
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
I would do :
SELECT t.*
FROM (SELECT p.projno, e.sal, e.ename,
DENSE_RANK() OVER (PARTITION BY p.projno ORDER BY e.sal DESC) AS Seq
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) t
WHERE Seq = 1;
EDIT : If you want to do it with correlated subquery then i would rewrite your query to make correlated :
SELECT p.projno, e.sal, e.ename
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
WHERE e.sal = (SELECT MAX(e1.sal)
FROM emp e1 INNER JOIN
proj_emp p1
ON e1.empno = p1.empno
WHERE p1.projno = p.projno
);
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
edited Nov 12 at 11:50
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
answered Nov 12 at 11:40
Yogesh Sharma
28k51335
28k51335
I forgot to mention, that in exercise instruction it was said to write correlated subquery inWHEREclause
– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but acorrelated subqueryis required. I useduncorrelated subquery
– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
add a comment |
I forgot to mention, that in exercise instruction it was said to write correlated subquery inWHEREclause
– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but acorrelated subqueryis required. I useduncorrelated subquery
– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
I forgot to mention, that in exercise instruction it was said to write correlated subquery in
WHERE clause– MartinKitty
Nov 12 at 11:43
I forgot to mention, that in exercise instruction it was said to write correlated subquery in
WHERE clause– MartinKitty
Nov 12 at 11:43
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
@MartinKitty. . . You have a already done that task.
– Yogesh Sharma
Nov 12 at 11:46
I know, but a
correlated subquery is required. I used uncorrelated subquery– MartinKitty
Nov 12 at 11:48
I know, but a
correlated subquery is required. I used uncorrelated subquery– MartinKitty
Nov 12 at 11:48
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
Great! That is a solution, that i was looking for!
– MartinKitty
Nov 12 at 11:57
add a comment |
1
Use window functions:
SELECT projno, sal, ename
FROM (SELECT p.projno, e.sal, e.ename,
MAX(e.sal) OVER (PARTITION BY p.projno) as max_sal
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) ps
WHERE sal = max_sal;
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
add a comment |
1
Use window functions:
SELECT projno, sal, ename
FROM (SELECT p.projno, e.sal, e.ename,
MAX(e.sal) OVER (PARTITION BY p.projno) as max_sal
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) ps
WHERE sal = max_sal;
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
add a comment |
1
1
1
Use window functions:
SELECT projno, sal, ename
FROM (SELECT p.projno, e.sal, e.ename,
MAX(e.sal) OVER (PARTITION BY p.projno) as max_sal
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) ps
WHERE sal = max_sal;
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
Use window functions:
SELECT projno, sal, ename
FROM (SELECT p.projno, e.sal, e.ename,
MAX(e.sal) OVER (PARTITION BY p.projno) as max_sal
FROM emp e INNER JOIN
proj_emp p
ON e.empno = p.empno
) ps
WHERE sal = max_sal;
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
answered Nov 12 at 11:37
Gordon Linoff
755k35290397
755k35290397
add a comment |
add a comment |
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Were you also asked to do this without window functions?
– Salman A
Nov 12 at 11:42
In an exercise instruction all what was said was to names of employees with the highest salaries for each project with a correlated subquery in a
WHEREcaluse– MartinKitty
Nov 12 at 11:46