Database Development
ORACLE
(SQL Components)
DDL
DML
JL_D.B.
DCL
(Retrieve Data and
Produce Information
from Multiple Tables)
Dr. Chen, Oracle Database System (Oracle)
1
Chapter 9
Joining Data from Multiple
Tables
(p.284-296; p.312-330)
Jason C. H. Chen, Ph.D.
Professor of MIS
School of Business
Gonzaga University
Spokane, WA 99258 USA
chen@jepson.gonzaga.edu
Dr. Chen, Oracle Database System (Oracle)
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Objectives
•
•
•
•
Identify a Cartesian join
Create an equality join using the WHERE clause
Create an equality join using the JOIN keyword
Create a non-equality join using the WHERE
clause
• Create a non-equality join using the JOIN…ON
approach
Dr. Chen, Oracle Database System (Oracle)
3
Objectives (continued)
•
•
•
•
•
Create a self-join using the WHERE clause
Create a self-join using the JOIN keyword
Distinguish an inner join from an outer join
Create an outer join using the WHERE clause
Create an outer join using the OUTER
keyword
• Use set operators to combine the results of
multiple queries
Dr. Chen, Oracle Database System (Oracle)
4
Creating additional Tables for chapter 9
• Run the following command for creating
additional tables:
SQL>start c:\oradata\chapter9\JLDB_Build_9.sql
• The following new four tables will be added
to your database (see next slide for details):
– Warehouses,
– Publisher2, Publisher3 and
– Employees
Dr. Chen, Oracle Database System (Oracle)
5
Additional Database for chapter 9
pk
warehouses
wh_id
NUMBER(2)
pk
warehouses
location
VARCHAR2(12)
Publishe2
ID
NUMBER(2)
pk
Name
VARCHAR2(23)
Contact
VARCHAR2(15)
Phone
VARCHAR2(12)
Publishe3
ID
Name
Contact
Phone
NUMBER(2)
VARCHAR2(23)
VARCHAR2(15)
VARCHAR2(12)
Publishe2
pk
Do we really need
to create two
additional
Publisher tables
(i.e., Publisher2
and Publisher3) ?
Publishe3
Employees
EMPNO
LNAME
FNAME
JOB
HIREDATE
DEPTNO
MTHSAL
MGR
NUMBER(4)
VARCHAR2(20)
VARCHAR2(15)
VARCHAR2(19)
DATE
NUMBER(2)
NUMBER(7,2)
NUMBER(4)
Dr. Chen, Oracle Database System (Oracle)
6
Purpose of Joins
• Joins are used to link tables and reconstruct
data in a relational database
• Joins can be created through:
– Conditions in a WHERE clause
– Use of JOIN keywords in FROM clause
Dr. Chen, Oracle Database System (Oracle)
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How many records will be in the Cartesian Join?
Figure 9-1 Results of a Cartesian Product
Dr. Chen, Oracle Database System (Oracle)
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Cartesian Joins
• Created by omitting joining condition in the
WHERE clause or through CROSS JOIN
keywords in the FROM clause
• Results in every possible row combination
(m * n)
• They are useful when
– performing certain statistical procedures for
data analysis
Dr. Chen, Oracle Database System (Oracle)
9
Cartesian Join Example:
Omitted Condition
Q: Why
unintentional
Cartesian join is
produced?
A: Because Oracle
didn’t know what
data the two tables
had in common.
Q: How to solve
the problem?
(70 rows produced)
Figure 9-3
Producing an unintentional Cartesian join
Dr. Chen, Oracle Database System (Oracle)
A: Use of
Equality Joins (or
inner/simple/natu
ral).
-- chapter 9, Figure 9-3; p.288
SELECT title, name
FROM books, publisher;
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Cartesian Join Example:
CROSS (Cartesian) JOIN Keywords
-- chapter 9, Figure 9-2; p.287
SELECT isbn, title, location, '
FROM books, warehouses
ORDER BY location, title;
' Count
-- chapter 9, Figure 9-2b; p.287
SELECT count (location)
FROM books, warehouses
ORDER BY location, title;
(42 rows produced)
Figure 9-4
Using the CROSS JOIN keywords
Dr. Chen, Oracle Database System (Oracle)
-- chapter 9, Figure 9-4; p.289
SELECT isbn, title, location, ' ' Count
FROM books CROSS JOIN warehouses
ORDER BY location, title;
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Equality Joins
• Link rows through equivalent data that
exists in both tables
• Created by:
– Creating equivalency condition in the WHERE
clause
– Using NATURAL JOIN, JOIN…USING, or
JOIN…ON keywords in the FROM clause
Dr. Chen, Oracle Database System (Oracle)
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Joining Multiple Tables
• Join: combine data from multiple database tables
using foreign key references
• SELECT field1, field2, ...
FROM table1, table2
WHERE table1.joinfield = table2.joinfield
AND search_condition(s);
• If tables share field names, must prefix field in select
with table name (table1.field1, table2.field1)
• Join condition: part of where clause indicating how
tables are related (table1.foreign_key =
table2.primary key)
• Search conditions can be added to join condition using
AND operator
Dr. Chen, Oracle Database System (Oracle)
13
Inner Join (cont.)
Q: why
“Brown” is not
on the result?
-- Exatra example
SELECT s_id, s_last, s_first,
student.f_id, f_last
FROM student, faculty
WHERE student.f_id =
faculty.f_id;
Dr. Chen, Oracle Database System (Oracle)
S_ID
-----1
2
3
4
5
6
6 rows
Q: How many rows
will be produced if
“C-Join” is used?
S_LAST
S_FIRST F_ID F_LAST
-------- -------- ---- -------Jones
Tammy
1 Cox
Perez
Jorge
1 Cox
Marsh
John
1 Cox
Smith
Mike
2 Blanchard
Johnson Lisa
4 Sheng
Nguyen
Ni
3 Williams
selected.
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Natural Join – Inner Join
• It can be used when the tables have a single
commonly named and defined column.
-- Extra Example
SELECT s_id, s_last, s_first,
student.f_id, f_last
FROM student, faculty
WHERE student.f_id =
faculty.f_id;
S_ID
-----1
2
3
4
5
6
6 rows
S_LAST
S_FIRST F_ID F_LAST
-------- -------- ---- -------Jones
Tammy
1 Cox
Perez
Jorge
1 Cox
Marsh
John
1 Cox
Smith
Mike
2 Blanchard
Johnson Lisa
4 Sheng
Nguyen
Ni
3 Williams
selected.
-- Use NATURAL JOIN
SELECT s_id, s_last, s_first, f_id, f_last
FROM student NATURAL JOIN faculty;
Dr. Chen, Oracle Database System (Oracle)
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Equality Joins (Traditional Method):
WHERE Clause Example
Figure 9-6
An equality join
Dr. Chen, Oracle Database System (Oracle)
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Qualifying Column Names
• Columns in
both tables
must be
qualified
• Which table is
“pubid” from?
• Is it from
publisher or
books?
-- chapter 9, Figure 9-7(b); p.292
SELECT title, books.pubid,
name
FROM books, publisher
WHERE books.pubid =
Figure 9-7
publisher.pubid;
Dr. Chen, Oracle Database System (Oracle)
A “column ambiguously defined” error
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WHERE Clause Supports Join and Other Conditions
Figure 9-8
Including search and join conditions in a WHERE clause
-- Use aliases
-- chapter 9, Figure 9-9; p.294
SELECT b.title, b.pubid, p.name
FROM books b, publisher p
WHERE b.pubid = p.pubid
AND (b.cost < 15 OR p.pubid = 1)
ORDER BY title;
Dr. Chen, Oracle Database System (Oracle)
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Using a Query Design Diagram
• Helpful for creating complicated queries
• Can use a formula to derive actual query from diagram
Query: Display customers’ lastname, firstname and
books’ title they purchased
Customers
Orders
Orderitems
Books
•customer# (j)
•lastname (d)
•firstname (d)
•order# (j)
•customer# (j)
•order# (j)
•isbn (j)
•isbn (j)
•title (d)
j: join
s: search
d: display
Dr. Chen, Oracle Database System (Oracle)
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Query: Display customers’ lastname, firstname and
books’ title they purchased
Customers
Orders
Orderitems
Books
•customer# (j)
•lastname (d)
•firstname (d)
•order# (j)
•customer# (j)
•order# (j)
•isbn (j)
•isbn (j)
•title (d)
Figure: Join query design diagram
j: join
s: search
You can derive your query from the diagram by following these
steps:
d: display
1. Place the display fields in the SELECT clause
2. List all of the tables in the FROM clause
3. Include the links in join conditions in the WHERE clause
4. Include all of the search fields in the WHERE clause (if needed)
Dr. Chen, Oracle Database System (Oracle)
20
Query: Display customers’ lastname, firstname and
books’ title they purchased
Customers
Orders
Orderitems
Books
•customer# (j)
•lastname (d)
•firstname (d)
•order# (j)
•customer# (j)
•order# (j)
•isbn (j)
•isbn (j)
•title (d)
Figure: Join query design diagram
j: join
s: search
d: display
-- chapter 9, Figure 9-10; p.295
SELECT c.lastname, c.firstname, b.title
FROM customers c, orders o, orderitems oi, books b
WHERE c.customer# = o.customer#
AND o.order# = oi.order#
AND oi.isbn = b.isbn
ORDER BY lastname, firstname;
Dr. Chen, Oracle Database System (Oracle)
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Joining More Than Two Tables
• Joining
four tables
requires
three join
conditions
• Joining N
tables
requires
___ join
conditions
Figure 9-10 Joining four tables
Dr. Chen, Oracle Database System (Oracle)
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Query: Display customers’ lastname, firstname and
books’ title and only in ‘COMPUTER’ category
Customers
Orders
Orderitems
Books
•customer# (j)
•lastname (d)
•firstname (d)
•order# (j)
•customer# (j)
•order# (j)
•isbn (j)
•isbn (j)
•title (d)
category (s)
• _______
Figure: Join query design diagram
j: join
s: search
d: display
-- chapter 9, Figure 9-10; p.295
SELECT c.lastname, c.firstname, b.title
FROM customers c, orders o, orderitems oi, books b
WHERE c.customer# = o.customer#
AND o.order# = oi.order#
AND oi.isbn = b.isbn
AND category = ‘COMPUTER’
ORDER BY lastname, firstname;
Dr. Chen, Oracle Database System (Oracle)
23
Equality Joins: NATURAL JOIN
Figure 9-12 Using the NATURAL JOIN keywords
Dr. Chen, Oracle Database System (Oracle)
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No Qualifiers with a NATURAL JOIN
Figure 9-13 Column qualifier error with a NATURAL JOIN
Natural Join keyword (e.g, pubid), we are not required to be specified
when the two tables have it in common.
Therefore most developers avoid using a NATURAL JOIN because it
can cause unexpected results.
Dr. Chen, Oracle Database System (Oracle)
25
Equality Joins: JOIN…USING
Figure 9-14
Performing
a join with
the JOIN …
USING
keywords
Dr. Chen, Oracle Database System (Oracle)
26
Break
• Assignments (#2 & #5 on p. 329; see at the end of
the slides)
• Figure out how to produce the output with ‘$’
displayed (below is a sample output for #5, p.329)
– hint:
• a) column …
• b) TO_CHAR (see p.365-367 and ‘learning to learn’)
TITLE
PROFIT
------------------------------ -------PAINLESS CHILD-REARING
$37.45
HOW TO MANAGE THE MANAGER
$16.55
PAINLESS CHILD-REARING
$37.45
TO_CHAR( PROFIT, _______ )
Dr. Chen, Oracle Database System (Oracle)
27
Query: list all author IDs with books in the ‘Family Life’ category
SELECT ba.authorid
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = 'FAMILY LIFE‘;
Query: list all author IDs with books in the ‘Children’ category
SELECT ba.authorid
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = 'CHILDREN';
Dr. Chen, Oracle Database System (Oracle)
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Query: list all author IDs with books in the ‘Family Life’ or
‘Children’ category
-- chapter 9, Figure 9-28; p. 313(version 1)
SELECT ba.authorid
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = ‘FAMILY LIFE’
OR category = ‘CHILDREN’;
Anything not appropriate in the output?
How to take care this type of
problem in an easy way?
-- chapter 9, Figure 9-28; p. 313(version 2)
SELECT _______ (ba.authorid)
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = 'FAMILY LIFE'
OR category = 'CHILDREN';
Dr. Chen, Oracle Database System (Oracle)
What else we can achieve the
same goal (and other more
complicated situation) ?
29
Using Set Operators to Combine Query
Results
• Performs set operations on outputs of two
unrelated queries
• They all require that both queries
– have the same number of display fields in the
SELECT statement, and that
– each field in the first query has the same data
type as the corresponding column in the second
query.
• <query 1> <SET Operator> <query 2>
Dr. Chen, Oracle Database System (Oracle)
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SET THEORY
A
Dr. Chen, Oracle Database System (Oracle)
B
31
SET THEORY
A
C
A-B
B-A
B
=A-B
=B-A
Dr. Chen, Oracle Database System (Oracle)
=A INTERSECT B= C
All Regions
=A UNION B
(with C counted just once)
32
SET THEORY
A
D
C
E
B
A MINUS B=D
A INTERSECT B= C
B MINUS A=E A UNION
Dr. Chen, Oracle Database System (Oracle)
B = D+C+E
C
A UNION ALL B = D+C+E+__
33
Oracle 11g/SQL Set Operator (Table 9-2)
Use to select data from multiple tables not connected
with foreign key relationships
Used to combine the results of two or more SELECT
statements
• UNION (see Figure 9-28)
– returns all rows from both queries, but ONLY displays
duplicate rows once
• UNION ALL (see Figure 9-30)
– returns all (duplicate) rows from both queries, and displays
ALL duplicate rows
• INTERSECT (see Figure 9-34)
– returns all matching rows that are returned by both queries
• MINUS (see Figure 9-35)
– returns all rows returned by the first query minus the
matching rows returned by the second query
Dr. Chen, Oracle Database System (Oracle)
34
Query: list all author IDs with books in the ‘Family Life’ or
‘Children’ category
SELECT ba.authorid
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = 'FAMILY LIFE‘
UNION
SELECT ba.authorid
FROM books b JOIN bookauthor ba
USING (isbn)
WHERE category = 'CHILDREN';
Figure 9-28 Producing an unduplicated combined list
with the UNION set operator
Dr. Chen, Oracle Database System (Oracle)
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Set Operators: UNION and UNION ALL Examples
What is the “difference” on the outputs?
Dr. Chen, Oracle Database System (Oracle)
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Query: list all customer numbers and those customers who have
placed an order recently
SELECT customer#
FROM customers
INTERSECT
SELECT customer#
FROM orders;
Figure 9-34 Identifying
overlapping values with the
INTERSECT set operator
Dr. Chen, Oracle Database System (Oracle)
37
Query: list all customer numbers but
haven’t placed an order recently
SELECT customer#
FROM customers
MINUS
SELECT customer#
FROM orders;
Figure 9-35 Subtract result sets
with the MINUS set operator
Dr. Chen, Oracle Database System (Oracle)
38
MORE EXAMPLES on SET OPERATORS
You need to run the following command
to make the example work:
@ c:\oradata\NW_CW\northwoods.sql
Query: A list of faculty members whose offices are in the BUS
building. (Extra example)
FACULTY
f_first (d)
f_last (d)
loc_id (j)
LOCATION
loc_id (j)
bldg_code (s)
SELECT f_first, f_last
FROM faculty, location
WHERE faculty.loc_id = location.loc_id
AND bldg_code = 'BUS';
Dr. Chen, Oracle Database System (Oracle)
39
Query: A list of faculty members who have taught a course in the
BUS building.
FACULTY
f_first (d)
f_last (d)
f_id (j)
COURSE_
SECTION
f_id (j)
loc_id (j)
LOCATION
loc_id (j)
bldg_code (s)
SELECT DISTINCT f_first, f_last
FROM faculty, location, course_section
WHERE faculty.f_id = course_section.f_id
AND location.loc_id = course_section.loc_id
AND bldg_code = 'BUS';
Dr. Chen, Oracle Database System (Oracle)
40
Query: A list of faculty members whose offices are in the BUS
building or who have taught a course in the BUS building. (extra
example)
SELECT f_first, f_last
FROM faculty, location
WHERE faculty.loc_id = location.loc_id
AND bldg_code = 'BUS'
Office
in ‘BUS’
UNION
SELECT f_first, f_last
FROM faculty, location, course_section
WHERE faculty.f_id = course_section.f_id
AND location.loc_id = course_section.loc_id
AND bldg_code = 'BUS';
Dr. Chen, Oracle Database System (Oracle)
Taught
courses
in ‘BUS’
41
Query: A list of faculty members whose offices are in the BUS
building and who have taught a course in the BUS building.
(extra example)
SELECT f_first, f_last
FROM faculty, location
WHERE faculty.loc_id = location.loc_id
AND bldg_code = 'BUS'
Office
in ‘BUS’
INTERSECT
SELECT f_first, f_last
FROM faculty, location, course_section
WHERE faculty.f_id = course_section.f_id
AND location.loc_id = course_section.loc_id
AND bldg_code = 'BUS';
Dr. Chen, Oracle Database System (Oracle)
Taught
courses
in ‘BUS’
42
And NEXT ...
Query: A list of faculty members who have taught a course in the
BUS building, but whose office are NOT located in the BUS
SELECT f_first, f_last
FROM faculty, location, course_section
WHERE faculty.f_id = course_section.f_id
AND location.loc_id = course_section.loc_id
AND bldg_code = 'BUS';
MINUS
SELECT f_first, f_last
FROM faculty, location
WHERE faculty.loc_id = location.loc_id
AND bldg_code = 'BUS'
Dr. Chen, Oracle Database System (Oracle)
Taught
courses
in ‘BUS’
Office
in ‘BUS’
43
• Practice all the examples in the text.
• A Script file is available on the Bb (file
name: ch9Queries.sql)
• After completing all examples, do the HW.
Dr. Chen, Oracle Database System (Oracle)
44
Bonus Assignment
--****************************************************************
-- Marketing department is analyzing books that don't sell.
-- A list of ISBNs and Book Titles for all books is needed.
-- Use a set operation (based on JL_Database to complete this task.
--****************************************************************
-- a sample solution
ISBN
TITLE
---------- -----------------------------0132149871 HOW TO GET FASTER PIZZA
0299282519 THE WOK WAY TO COOK
4981341710 BUILDING A CAR WITH TOOTHPICKS
Dr. Chen, Oracle Database System (Oracle)
45
Homework - Hands-On Assignments
Upload the WORD file (includes the Query Design
Diagrams)to the Bb (under “Assignments & Projects”) by the
deadline.
Read and Practice all examples on Chapters 9
• 1. Run the script files (in the folder \oradata\chapter9\):
JLDB_Build_9.sql
• 2a. Read Oracle assignment and create a script file
Oracle_ch9_Lname_Fname.sql for questions (#2 & #5 ; p.329)
on “Hands-on Assignments” (use TWO SQL queries, traditional
one and with “JOIN” read instructions carefully)
• 2b. Be sure to use i) traditional method, ii) JOIN keyword, iii)
draw Query Design Diagrams for each problem, and iv) use
COLUMN statement to produce readable outputs – see next slide
for details
• 3. Execute and test one problem at a time and make sure they are
all running successfully.
• 4. When you done, spool the script files (see next slide for spooling
instructions) and UPLOAD the WORD file including the Query
Design Diagrams (see detail on the next slide) to Bb by the
deadline.
Dr. Chen, Oracle Database System (Oracle)
46
How to Spool your Script and Output Files and
add Query Design Diagrams
After you tested the script file of Oracle_ch9_Lname_Fname.sql successfully,
follow the instructions below to spool both script and output files:
Step 0. Run the following script file from SQL*Plus (since you have created
JLDB tables)
– Start c:\oradata\chapter9\JLDB_Build_9.sql
• 1. type the following on SQL>
– Spool c:\oradata\Oracle_ch9_Spool_Lname_Fname.txt (make sure
your name is entered)
• 2. open Oracle_ch9_Lname_Fname.sql that you already tested
• 3. copy and paste all the SQL commands (including all comments) to the
SQL*PLUS
• 4. type Spool Off on the SQL>
The output should contain your personal information, all SQL commands and
their solution on the .txt file and saved in C: drive (oradata\folder).
Be sure that COLUMN commands might be needed on the script file to align
the output.
Dr. Chen, Oracle Database System (Oracle)
47
How to Spool your Script and Output Files and
add Query Design Diagrams (continued)
•
5. Next, you should use MS/Word to open the *.txt file and
include/DRAW “Query Design Diagram” figures for queries
with multiple tables. You may use font of “Courier new” to
align the output.
• 6. Save it as *.docx file.
Upload the WORD file (includes the Query Design
Diagrams)to the Bb (under “Assignments &
Projects”) by the deadline.
Dr. Chen, Oracle Database System (Oracle)
48
Summary
• Data stored in multiple tables regarding a single
entity can be linked together through the use of
joins
• A Cartesian join between two tables returns every
possible combination of rows from the tables; the
resulting number of rows is always m * n
• An equality join is created when the data joining
the records from two different tables are an exact
match
• A non-equality join establishes a relationship based
upon anything other than an equal condition
• Self-joins are used when a table must be joined to
itself to retrieve needed data
Dr. Chen, Oracle Database System (Oracle)
49
Summary (continued)
• Inner joins are categorized as being equality, nonequality, or self-joins
• An outer join is created when records need to be
included in the results without having
corresponding records in the join tables
– The record is matched with a NULL record so it will be
included in the output
• Set operators such as UNION, UNION ALL,
INTERSECT, and MINUS can be used to
combine the results of multiple queries
Dr. Chen, Oracle Database System (Oracle)
50