Copyright Oracle Corporation, 1998. All rights reserved.

77

Multiple-Column SubqueriesMultiple-Column Subqueries

7-2 Copyright Oracle Corporation, 1998. All rights reserved.

ObjectivesObjectives

After completing this lesson, you should After completing this lesson, you should be able to do the following:be able to do the following:

• Write a multiple-column subquery

• Describe and explain the behavior of subqueries when null values are retrieved

• Write a subquery in a FROM clause

After completing this lesson, you should After completing this lesson, you should be able to do the following:be able to do the following:

• Write a multiple-column subquery

• Describe and explain the behavior of subqueries when null values are retrieved

• Write a subquery in a FROM clause

7-3 Copyright Oracle Corporation, 1998. All rights reserved.

Multiple-Column SubqueriesMultiple-Column Subqueries

Main query

MANAGER 10

Subquery

SALESMAN 30

MANAGER 10

CLERK 20

Main queryMain querycomparescompares

MANAGER 10MANAGER 10

Values from a multiple-row andValues from a multiple-row andmultiple-column subquerymultiple-column subquery

SALESMAN SALESMAN 3030

MANAGER MANAGER 1010

CLERK CLERK 2020

toto

7-4 Copyright Oracle Corporation, 1998. All rights reserved.

Using Multiple-Column Subqueries

Using Multiple-Column Subqueries

Display the order number, product number, and Display the order number, product number, and quantity of any item in which the product quantity of any item in which the product number and quantity match number and quantity match bothboth the product the product number and quantity of an item in order 605.number and quantity of an item in order 605.

Display the order number, product number, and Display the order number, product number, and quantity of any item in which the product quantity of any item in which the product number and quantity match number and quantity match bothboth the product the product number and quantity of an item in order 605.number and quantity of an item in order 605.

SQL> SELECT ordid, prodid, qty 2 FROM item 3 WHERE (prodid, qty) IN 4 (SELECT prodid, qty 5 FROM item 6 WHERE ordid = 605) 7 AND ordid <> 605;

7-6 Copyright Oracle Corporation, 1998. All rights reserved.

Pair wisePair wise

select ename,deptno,salselect ename,deptno,sal

from empfrom emp

where (deptno,sal) in (select deptno,sal where (deptno,sal) in (select deptno,sal from empfrom emp

where comm is not null);where comm is not null);

select ename,deptno,salselect ename,deptno,sal

from empfrom emp

where (deptno,sal) in (select deptno,sal where (deptno,sal) in (select deptno,sal from empfrom emp

where comm is not null);where comm is not null);

7-7 Copyright Oracle Corporation, 1998. All rights reserved.

Column ComparisonsColumn Comparisons

Pairwise

PRODID QTY

101863 100

100861 100

102130 10

100890 5

100870 500

101860 50

Nonpairwise

PRODID QTY

101863 100

100861 100

102130 10

100890 5

100870 500

101860 50

7-8 Copyright Oracle Corporation, 1998. All rights reserved.

Nonpairwise Comparison Subquery

Nonpairwise Comparison Subquery

SQL> SELECT ordid, prodid, qty 2 FROM item 3 WHERE prodid IN (SELECT prodid 4 FROM item 5 WHERE ordid = 605) 6 AND qty IN (SELECT qty 7 FROM item 8 WHERE ordid = 605) 9 AND ordid <> 605;

Display the order number, product number, and Display the order number, product number, and quantity of any item in which the product number quantity of any item in which the product number and quantity match any product number and any and quantity match any product number and any quantity of an item in order 605.quantity of an item in order 605.

Display the order number, product number, and Display the order number, product number, and quantity of any item in which the product number quantity of any item in which the product number and quantity match any product number and any and quantity match any product number and any quantity of an item in order 605.quantity of an item in order 605.

7-9 Copyright Oracle Corporation, 1998. All rights reserved.

Non Pair wiseNon Pair wise

select ename,deptno,salselect ename,deptno,sal

from empfrom emp

where deptno in (select deptno from emp where deptno in (select deptno from emp where comm is not null)where comm is not null)

and sal in (select sal from emp where and sal in (select sal from emp where comm is not null);comm is not null);

select ename,deptno,salselect ename,deptno,sal

from empfrom emp

where deptno in (select deptno from emp where deptno in (select deptno from emp where comm is not null)where comm is not null)

and sal in (select sal from emp where and sal in (select sal from emp where comm is not null);comm is not null);

7-10 Copyright Oracle Corporation, 1998. All rights reserved.

Nonpairwise SubqueryNonpairwise Subquery

ORDID PRODID QTY--------- --------- --------- 609 100870 5 616 100861 10 616 102130 10 621 100861 10 618 100870 10 618 100861 50 616 100870 50 617 100861 100 619 102130 100 615 100870 100 617 101860 100 621 100870 100 617 102130 100 . . . 16 rows selected.

7-11 Copyright Oracle Corporation, 1998. All rights reserved.

Null Values in a SubqueryNull Values in a Subquery

SQL> SELECT employee.ename 2 FROM emp employee 3 WHERE employee.empno NOT IN 4 (SELECT manager.mgr 5 FROM emp manager);no rows selected.no rows selected.

7-12 Copyright Oracle Corporation, 1998. All rights reserved.

Using a Subquery in the FROM ClauseUsing a Subquery

in the FROM Clause

ENAME SAL DEPTNO SALAVG---------- --------- --------- ----------KING 5000 10 2916.6667JONES 2975 20 2175SCOTT 3000 20 2175...6 rows selected.

ENAME SAL DEPTNO SALAVG---------- --------- --------- ----------KING 5000 10 2916.6667JONES 2975 20 2175SCOTT 3000 20 2175...6 rows selected.

SQL> SELECT a.ename, a.sal, a.deptno, b.salavg 2 FROM emp a, (SELECT deptno, avg(sal) salavg 3 FROM emp 4 GROUP BY deptno) b 5 WHERE a.deptno = b.deptno 6 AND a.sal > b.salavg;

7-13 Copyright Oracle Corporation, 1998. All rights reserved.

Correlated SubqueryCorrelated Subquery

The outer Query is executed first and then The outer Query is executed first and then the inner query is executed.the inner query is executed.

Find the employee list who earn more Find the employee list who earn more than the avg salary of their own than the avg salary of their own departmentdepartment

Example:Example:

Select * from emp XSelect * from emp X

Where sal > (Select avg(sal) from emp Where sal > (Select avg(sal) from emp where x.deptno=deptno)where x.deptno=deptno)

The outer Query is executed first and then The outer Query is executed first and then the inner query is executed.the inner query is executed.

Find the employee list who earn more Find the employee list who earn more than the avg salary of their own than the avg salary of their own departmentdepartment

Example:Example:

Select * from emp XSelect * from emp X

Where sal > (Select avg(sal) from emp Where sal > (Select avg(sal) from emp where x.deptno=deptno)where x.deptno=deptno)

7-14 Copyright Oracle Corporation, 1998. All rights reserved.

Exists operatorExists operator

Find the list of employees who has Find the list of employees who has subordinates.subordinates.

Select * from emp eSelect * from emp e

Where exists(select 'X' from empWhere exists(select 'X' from emp

Where mgr=e.empno);Where mgr=e.empno);

Find the list of employees who has Find the list of employees who has subordinates.subordinates.

Select * from emp eSelect * from emp e

Where exists(select 'X' from empWhere exists(select 'X' from emp

Where mgr=e.empno);Where mgr=e.empno);

7-15 Copyright Oracle Corporation, 1998. All rights reserved.

Exists alternativeExists alternative

Select * from empSelect * from emp

Where empno in (select mgr from emp Where empno in (select mgr from emp where mgr is not null);where mgr is not null);

select distinct a.ename from emp a,emp bselect distinct a.ename from emp a,emp b

where a.empno=b.mgr;where a.empno=b.mgr;

select empno from emp where empno in select empno from emp where empno in (select mgr from emp);(select mgr from emp);

Select * from empSelect * from emp

Where empno in (select mgr from emp Where empno in (select mgr from emp where mgr is not null);where mgr is not null);

select distinct a.ename from emp a,emp bselect distinct a.ename from emp a,emp b

where a.empno=b.mgr;where a.empno=b.mgr;

select empno from emp where empno in select empno from emp where empno in (select mgr from emp);(select mgr from emp);

7-16 Copyright Oracle Corporation, 1998. All rights reserved.

Not ExistsNot Exists

Find the list of employees who has Find the list of employees who has managermanager

Select * from emp eSelect * from emp e

Where not exists(select 'X' from empWhere not exists(select 'X' from emp

Where mgr=e.empno)Where mgr=e.empno)

Find the list of employees who has Find the list of employees who has managermanager

Select * from emp eSelect * from emp e

Where not exists(select 'X' from empWhere not exists(select 'X' from emp

Where mgr=e.empno)Where mgr=e.empno)

7-17 Copyright Oracle Corporation, 1998. All rights reserved.

Non Exists AlternativeNon Exists Alternative

Select * from empSelect * from emp

Where empno not in (select mgr from emp Where empno not in (select mgr from emp where mgr is not null)where mgr is not null)

Select * from empSelect * from emp

Where empno not in (select mgr from emp Where empno not in (select mgr from emp where mgr is not null)where mgr is not null)

7-18 Copyright Oracle Corporation, 1998. All rights reserved.

SummarySummary

• A multiple-column subquery returns more than one column.

• Column comparisons in multiple- column comparisons can be pairwise or nonpairwise.

• A multiple-column subquery can also be used in the FROM clause of a SELECT statement.

• A multiple-column subquery returns more than one column.

• Column comparisons in multiple- column comparisons can be pairwise or nonpairwise.

• A multiple-column subquery can also be used in the FROM clause of a SELECT statement.

7-19 Copyright Oracle Corporation, 1998. All rights reserved.

Practice OverviewPractice Overview

Creating multiple-column subqueriesCreating multiple-column subqueries