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)
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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
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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
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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
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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
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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)
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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
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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
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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
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-- 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
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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
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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. 14
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
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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 17
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)
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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 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;
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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;
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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)
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Equality Joins: JOIN…USING Figure 9-14 Performing a join with the JOIN … USING keywords
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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)
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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';
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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.
•
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SET THEORY
A
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B
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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)
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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+__
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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)
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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
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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
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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
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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)
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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)
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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.
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Homework - Hands-On Assignments Email me with one attachment (Oracle_ch9_Spool_Lname_Fname.) to:
[email protected] with subject title of Bmis441-01_Oracle_ch9 (or Bmis441-02_Oracle_ch9) 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 email the file • 5. Include Query Design Diagrams Dr. Chen, Oracle Database System (Oracle)
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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
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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)
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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.
Email me with the *.doc (or *.docx) file that includes all required documents with attachment to:
[email protected] with subject title of Bmis441-01_Oracle_ch9 (or Bmis441-02_Oracle_ch9)
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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)
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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
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