Download Query Joins

Inner Join vs. Outer Join
Information Retrieval from
Relational Databases
1
Query Languages
• Relational Algebra
• Three main operators: Select, Project, Join
• Provides the conceptual basis for SQL and QBE
• Structured Query Language (SQL)
• The user enters commands according to a predefined syntax to retrieve desired data.
• Query By Example (QBE)
• The user starts with a sample of the table(s)
columns and marks the fields he or she wants to
include in the answer.
• Defaults are available for summarizing and
manipulating the data.
2
SQL (Structured Query Language)
• Each query statement follows the same
structure:
SELECT attribute name(s)
FROM table name(s)
WHERE criteria is met;
3
Relational Algebra
• Select
• includes only certain rows from a database
table in its “answer”.
• Project
• includes only certain columns from a
database table in its “answer”
• Join
• combines two or more database tables on
the basis of one or more common attributes
4
Join Types
• Inner join(default in access)
• includes only the records from both tables
that have the exact same values in the fields
that are joined
• I.e.,
• Outer join
• includes all records from one table, and
matches those records from the other table
for which values in the joined fields are
equal
Right Outer Join
• I.e., Left Outer Join
5
Example Tables
Employee
EmplD
SocialSec#
E1
123345678
E2
234456789
E3
345567890
E4
456678901
E5
567789101
E6
678891012
Department
DepartmentID
D1
D2
D3
D4
LastName
Adams
Boston
Crabb
Davis
Engler
Folkert
FirstName
Anita
Benjamin
Charlie
Deborah
Edward
Fawn
Street Address
144 Apple St.
255 Banana Rd.
366 Cherry Ave.
477 Dip Dr.
588 Eggplant St.
699 Fruity Ave.
Pay rate Telephone
$10.00 555-1234
$12.00 555-2345
$14.00 555-3456
$32.00 555-4567
$11.00 555-5678
$23.00 555-6789
DeptID
D4
D2
D2
D1
D4
D3
TrainingCourse
Name
Executive Management
Accounting
Information Systems
Operations
CourseID
AC1
AC2
IS1
IS2
MD100
Description
Accounting Fundamentals
Chart of Accounts
Basic Information Systems
Database Design
ERP Systems
Length
2 days
5 days
5 days
5 days
10 days
CourseTaken
EmplID
E3
E3
E4
E6
E6
CourseID
AC1
AC2
AC1
IS1
IS2
DateTaken
May 1-2
June 24-28
Oct 14-15
June 24-28
July 8-12
6
Relationship View
7
Query to List ALL Employees and Description
of any Training Courses Taken ( Inner Join)
8
Example Tables
Note: We have 6 employees
Employee
EmplD
SocialSec#
E1
123345678
E2
234456789
E3
345567890
E4
456678901
E5
567789101
E6
678891012
Department
DepartmentID
D1
D2
D3
D4
LastName
Adams
Boston
Crabb
Davis
Engler
Folkert
FirstName
Anita
Benjamin
Charlie
Deborah
Edward
Fawn
Street Address
144 Apple St.
255 Banana Rd.
366 Cherry Ave.
477 Dip Dr.
588 Eggplant St.
699 Fruity Ave.
Pay rate Telephone
$10.00 555-1234
$12.00 555-2345
$14.00 555-3456
$32.00 555-4567
$11.00 555-5678
$23.00 555-6789
DeptID
D4
D2
D2
D1
D4
D3
TrainingCourse
Name
Executive Management
Accounting
Information Systems
Operations
CourseID
AC1
AC2
IS1
IS2
MD100
Description
Accounting Fundamentals
Chart of Accounts
Basic Information Systems
Database Design
ERP Systems
Length
2 days
5 days
5 days
5 days
10 days
CourseTaken
EmplID
E3
E3
E4
E6
E6
CourseID
AC1
AC2
AC1
IS1
IS2
DateTaken
May 1-2
June 24-28
Oct 14-15
June 24-28
July 8-12
9
Does this This Give Us What we Need?
LastName
Crabb
Crabb
Folkert
Folkert
Davis
FirstName
Charlie
Charlie
Fawn
Fawn
Deborah
CourseID
AC1
AC2
IS1
IS2
AC1
Description
Accounting Fundamentals
Chart of Accounts
Basic Information Systems
Database Design
Accounting Fundamentals
The above based upon the default join which
is the inner join and will not give us
employees that have not taken training
classes
SQL code created by access for QBE on previous slide
10
Using Outer Joins
Note change
11
LastName
Adams
Boston
Crabb
Crabb
Davis
Engler
Folkert
Folkert
FirstName
Anita
Benjamin
Charlie
Charlie
Deborah
Edward
Fawn
Fawn
CourseID
Description
AC1
AC2
AC1
Accounting Fundamentals
Chart of Accounts
Accounting Fundamentals
IS1
IS2
Basic Information Systems
Database Design
SQL code created by access for QBE on previous slide
12
The Revenue Cycle of M&M
M&M sells its agleclaps to customers through a
network of company salespeople. Each type of
agleclap is bought from a particular vendor and is
given an initial list price. Each salesperson services a
separate group of customers and is allowed to offer
them various discounts from list to induce sales. Each
sale can include one or more types of agleclaps and
can be paid for in any one of three ways: (1)
immediately in cash, (2) on the 15th of the following
month, or (3) over the course of six months. When
cash is received, a cashier deposits it into a company
bank account. Sales are signaled by invoices; cash
receipts by remittance advices
13
(0, N)
M
Sale-lineitem
(1, N)
(1, 1)
SALE
N
N
(0, N)
SALE
Inside
party
(0, N)
HIGHEST-DEGREE
NAME
MONTHLYPAY
EMPLOYEE #
SALE-AMOUNT
SALE-DATE
INVOICE #
ACTUAL-PRICE-OFEACH-AGLECLAP
QUANTITY-SOLD
QOH
LIST PRICE
DESCRIPTION
AGLECLAP
PRIMARY
VENDOR
INVENTORY
M & M Revenue Cycle
REA Model
SALESPERSON
QUARTERLY SALES
EMPLOYEE
1
(0, N)
(1, 1)
(1, 1)
1
N
N
M
SALEOutside
Party
Kind
of
Services
CUSTOMER #
(0, N)
AMOUNT-OFRECEIPT-APPLIEDTO-SALE
SALESPERSON
COMMISSION
RATE
FIDELITY BOND
RATING
N
Salepayment
(1, 1)
1
CUSTOMERNAME
CUSTOMER
(0, N)
A/RAMOUNT
(0, N)
1
(0, N)
N
1
CR
Outside
Party
EMPLOYEE-CATEGORY
NUMBER-OFEMPLOYEES
(0, 1)
MEDICAL-PLAN
N
N
CASH
RECEIPT
RECEIPT-DATE
(1, 1)
CASH-RECEIPTAMOUNT
1
CashInflow
REMITTANCEADVICE #
(0, N)
ACCOUNTTYPE
ACCOUNTBALANCE
BANK
BANKACCOUNT #
CASH
(1, 1)
N
CR
Inside
Party
(0, N)
1
EMPLOYEE
EMPLOYEE
CATEGORY
Relationship View
15
Example Tables (Incomplete Enterprise Database)
from Dunn & McCarthy (2004) working paper
Inventory-Sale Stockflow
Sale
Salesperson
Inventory Sale
Actual Sale# Amount Date
Cust# SalesRep#
Employee Quarterly Comm
ItemID
Number Quantity Price S-1
7,200 1 July
C-1
E-12
Number
Sales $
rate
A-4
S-1
2
600 S-2
10,000 21 July
C-2
E-10
E-12
.12
A-1
S-1
3 2,000 S-3
16,000 22 July
C-5
E-10
E-10
.10
A-6
S-2
2 5,000 S-4
10,000 26 July
C-2
E-10
E-99
.10
A-1
S-3
1 2,000 S-5
16,600 31 July
C-5
E-10
E-78
0
.15
A-5
S-3
2 4,000 S-6
35,000 15 Aug
C-3
E-10
A-3
S-3
6 1,000 S-7
23,000 21 Aug
C-4
E-99
A-6
S-4
2 5,000
Customer
Sale-CashRecDuality
A-2
S-5
2 3,000
Customer# Name A/R Amt
SP#
Sale#
RA#
Applied
A-4
S-5
2
300
C-1
Bill
E-12
S-2
RA-1
1,666
A-6
S-5
2 5,000
C-2
Mick
E-10
S-4
RA-2
10,000
A-2
S-6
10 3,500
C-3
Keith
E-10
S-1
RA-3
7,200
A-6
S-7
2 7,000
C-4
Charlie
E-99
S-3
RA-4
16,000
A-5
S-7
3 3,000
C-5
Ron
E-10
S-5
RA-4
16,600
S-2
RA-5
1,666
Cash
Account#
BA-6
BA-7
BA-8
BA-9
Type
Checking
Checking
Draft
Checking
Bank
Boston5
Shawmut
Shawmut
MassNat
Cash Receipt
Balance Remittance
Advice#
Amount
RA-1
1,666
10,000
75,000 RA-2
7,200
0 RA-3
RA-4
32,600
RA-5
1,666
Bank
Account#
BA-6
BA-7
BA-7
BA-7
BA-6
Date
25 July
26 July
15 Aug
15 Aug
25 Aug
Customer
Number
C-2
C-2
C-1
C-5
C-2
Cashier
Number
E-39
E-39
E-39
E-39
E-39
16
SQL and Relational Algebra
Inner Join vs. Outer Join
• Find all details of all sales and the cash
receipt number and amount applied of any
cash receipts related to those sales
• Data we need for this example is in 2 tables
• Summary sales totals have been stored in sales table
• If summary figure not stored, you would need also need the
sale-inventory relationship table to calculate sales totals
• Note: there have been no cash receipts related to sales
transaction 6 & 7.
Sale
Sale#
S-1
S-2
S-3
S-4
S-5
S-6
S-7
Amount Date
7,200 1 July
10,000 21 July
16,000 22 July
10,000 26 July
16,600 31 July
35,000 15 Aug
23,000 21 Aug
Cust# SalesRep#
C-1
E-12
C-2
E-10
C-5
E-10
C-2
E-10
C-5
E-10
C-3
E-10
C-4
E-99
Sale-CashRecDuality
Sale#
RA#
Applied
S-2
RA-1
1,666
S-4
RA-2
10,000
S-1
RA-3
7,200
S-3
RA-4
16,000
S-5
RA-4
16,600
S-2
RA-5
1,666
17
Relational Algebra Inner Join in QBE
Details of all sales, related cash receipts
18
Relational Algebra Inner Join in QBE
Details of all sales, related cash receipts
19
Default join is inner Join
If you double click on the join you will see
the join properties box.
Item 1, the inner join is the default
20
Inner Join Results
• Sales transactions 6 & 7 are not listed since there
was no cash receipts associated with them.
• Does this create a potential problem??
SELECT Sale.SaleNumber, Sale.Amount, Sale.Date, Sale.CustomerNumber, [SaleCashRecDuality].RemittanceAdviceNumber, [Sale-CashRecDuality].Applied FROM Sale
INNER JOIN [Sale-CashRecDuality] ON Sale.SaleNumber = [SaleCashRecDuality].SaleNumber;
21
Relational Algebra Outer Join in QBE
Details of all sales, related cash receipts
Double-click on
the join line
22
Relational Algebra Outer Join in QBE
Details of all sales, related cash receipts
Click on
appropriate join
type
Click OK
23
Relational Algebra Outer Join in QBE
Details of all sales, related cash receipts
Note change in Join line
24
Relational Algebra Outer Join in QBE
Details of all sales, related cash receipts
Result
25
Joins Compared
Outer Join
Inner Join
26