Database Management Systems
Chapter 5
Advanced Queries
and Subqueries
Jerry Post
McGraw-Hill/Irwin
Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.
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Tables
Animal
AnimalOrder
OrderID
OrderDate
ReceiveDate
SupplierID
ShippingCost
EmployeeID
Animal
OrderItem
OrderID
AnimalID
Cost
Breed
Category
Breed
Employee
Supplier
SupplierID
Name
ContactName
Phone
Address
ZipCode
CityID
City
CityID
ZipCode
City
State
AreaCode
Population1990
Population1980
Country
Latitude
Longitude
Merchandise
Order
PONumber
OrderDate
ReceiveDate
SupplierID
EmployeeID
ShippingCost
EmployeeID
LastName
FirstName
Phone
Address
ZipCode
CityID
TaxPayerID
DateHired
DateReleased
OrderItem
PONumber
ItemID
Quantity
Cost
AnimalID
Name
Category
Breed
DateBorn
Gender
Registered
Color
ListPrice
Photo
Sale
Category
SaleID
SaleDate
EmployeeID
CustomerID
SalesTax
Category
Registration
SaleAnimal
SaleID
AnimalID
SalePrice
Customer
CustomerID
Phone
FirstName
LastName
Address
ZipCode
CityID
SaleItem
Merchandise
ItemID
Description
QuantityOnHand
ListPrice
Category
SaleID
ItemID
Quantity
SalePrice
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Organization
 Harder Questions
 Subqueries
 Not In, LEFT JOIN
 UNION, Multiple JOIN columns, Recursive JOIN
 Other SQL Commands
 DDL: Data Definition Language
 DML: Data Manipulation Language
 OLAP
 Microsoft SQL Server
 Oracle
 Microsoft Access Crosstab
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Harder Questions
 How many cats are “instock” on 10/1/04?
 Which cats sold for more
than the average price?
 Which animals sold for more
than the average price of
animals in their category?
 Which animals have not
been sold?
 Which customers (who
bought something at least
once) did not buy anything
between 11/1/04 and
12/31/04?
 Which customers who
bought Dogs also bought
products for Cats (at any
time)?
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Sub-query for Calculation
 Which cats sold for more than the average sale price of cats?
 Assume we know the average price is $170.
 Usually we need to compute it first.
SELECT SaleAnimal.AnimalID, Animal.Category, SaleAnimal.SalePrice
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE ((Animal.Category=‘Cat’) AND (SaleAnimal.SalePrice>170));
SELECT SaleAnimal.AnimalID, Animal.Category, SaleAnimal.SalePrice
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE ((Animal.Category=‘Cat’) AND (SaleAnimal.SalePrice>
( SELECT AVG(SalePrice)
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE (Animal.Category=‘Cat’)
)
) );
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Query04_13
Query Sets (IN)
SELECT Customer.LastName, Customer.FirstName, SaleItem.ItemID
FROM (Customer INNER JOIN Sale ON Customer.CustomerID = Sale.CustomerID)
INNER JOIN SaleItem ON Sale.SaleID = SaleItem.SaleID
WHERE (SaleItem.ItemID In (1,2,30,32,33))
ORDER BY Customer.LastName, Customer.FirstName;
Customer
Sale
CustomerID
Phone
FirstName
LastName
SaleID
SaleDate
EmployeeID
CustomerID
Field
LastName
FirstName
ItemID
Table
Customer
Customer
SaleItem
Sort
Ascending
Ascending
Criteria
SaleItem
SaleID
ItemID
Quantity
SalePrice
In (1,2,30,32,33)
Or
List all customers (Name) who purchased one of the following
items: 1, 2, 30, 32, 33.
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Using IN with a Sub-query
 List all customers who bought items for cats.
SELECT Customer.LastName, Customer.FirstName, SaleItem.ItemID
FROM (Customer
INNER JOIN Sale ON Customer.CustomerID = Sale.CustomerID)
INNER JOIN SaleItem ON Sale.SaleID = SaleItem.SaleID
WHERE (SaleItem.ItemID In
(SELECT ItemID FROM Merchandise WHERE Category=‘Cat’)
);
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Query04_14
SubQuery (IN: Look up a Set)
SELECT Customer.LastName, Customer.FirstName
FROM Customer INNER JOIN Sale ON Customer.CustomerID = Sale.CustomerID
WHERE ((Month([SaleDate])=3)) And Customer.CustomerID In
(SELECT CustomerID
FROM Sale
WHERE (Month([SaleDate])=5) );
Customer
Sale
CustomerID
Phone
FirstName
LastName
SaleID
SaleDate
EmployeeID
CustomerID
LastName
Adkins
McCain
Grimes
First
Inga
Sam
Earl
Field
LastName
FirstName
Month(SaleDate)
CustomerID
Table
Customer
Customer
Sale
Customer
Sort
Ascending
Ascending
3
In (SELECT CustomerID FROM State
WHERE (Month(SaleDAte)=5)
Criteria
Or
List all of the customers who bought something in March and
who bought something in May. (Two tests on the same data!)
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Query04_15
SubQuery (ANY, ALL)
SELECT Animal.AnimalID, Name, SalePrice, ListPrice
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE ((SalePrice > Any
(SELECT 0.80*ListPrice
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE Category = ‘Cat’))
AND (Category=‘Cat’);
 Any: value is compared to each item in the list. If it is True for any of
the items, the statement is evaluated to True.
 All: value is compared to each item in the list. If it is True for every
item in the list, the statement is evaluated to True (much more
restrictive than any.
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Query04_16
SubQuery: NOT IN (Subtract)
Animal
AnimalID
Name
Category
Breed
SELECT Animal.AnimalID, Animal.Name, Animal.Category
FROM Animal
WHERE (Animal.AnimalID Not In
(SELECT AnimalID From SaleAnimal));
Field
AnimalID
Name
Category
Table
Animal
Animal
Animal
Sort
Criteria
Not In (SELECT AnimalID
FROM SaleAnimal)
Or
AnimalID
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25
34
88
181
Name
Leisha
Gene
Vivian
Rhonda
Brandy
Category
Dog
Dog
Dog
Dog
Dog
Fish
 Which animals have not been sold?
 Start with list of all animals.
 Subtract out list of those who were sold.
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SubQuery: NOT IN (Data)
Animal
ID
2
4
5
6
7
8
9
10
11
12
Name
Category
Fish
Gary
Dog
Fish
Rosie
Cat
Eugene Cat
Miranda Dog
Fish
Sherri
Dog
Susan
Dog
Leisha Dog
SaleAnimal
Breed
Angel
Dalmation
Shark
Oriental Shorthair
Bombay
Norfolk Terrier
Guppy
Siberian Huskie
Dalmation
Rottweiler
ID
2
4
6
7
8
10
11
SaleID SalePrice
35
$10.80
80
$156.66
27
$173.99
25
$251.59
4
$183.38
18
$150.11
17
$148.47
Which animals have not been sold?
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Query04_17
Left Outer Join
SELECT Animal.AnimalID, Animal.Name, Animal.Category
FROM Animal LEFT JOIN SaleAnimal
ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE (SaleAnimal.SaleID Is Null);
Animal
SaleAnimal
AnimalID
Name
Category
Breed
SaleID
AnimalID
SalePrice
Field
AnimalID
SaleID
Name
Category
Table
Animal
SaleAnimal
Animal
Animal
AnimalID
12
19
25
34
88
181
Name
Leisha
Gene
Vivian
Rhonda
Brandy
Category
Dog
Dog
Dog
Dog
Dog
Fish
Sort
Criteria
Is Null
Or
 Which animals have not been sold?
 LEFT JOIN includes all rows from left table (Animal)
 But only those from right table (SaleAnimal) that match a row in Animal.
 Rows in Animal without matching data in Sale Animal will have Null.
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Left Outer Join (Example)
ID
2
4
5
6
7
8
9
10
11
12
Name
Category
Fish
Gary
Dog
Fish
Rosie
Cat
Eugene Cat
Miranda Dog
Fish
Sherri
Dog
Susan
Dog
Leisha Dog
Breed
Angel
Dalmation
Shark
Oriental Shorthair
Bombay
Norfolk Terrier
Guppy
Siberian Huskie
Dalmation
Rottweiler
ID
2
4
Null
6
7
8
Null
10
11
Null
SaleID
35
80
Null
27
25
4
Null
18
17
Null
SalePrice
$10.80
$156.66
Null
$173.99
$251.59
$183.38
Null
$150.11
$148.47
Null
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Older Syntax for Left Join
 Which animals have not been sold?
SELECT ALL
FROM Animal, SaleAnimal
WHERE Animal.AnimalID *= SaleAnimal.AnimalID
And SaleAnimal.SaleID Is Null;
Old Oracle syntax—
note that the (+) symbol is on the reversed side.
SELECT ALL
FROM Animal, SaleAnimal
WHERE Animal.AnimalID = SaleAnimal.AnimalID (+)
And SaleAnimal.SaleID Is Null;
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Query04_18
SubQuery for Computation
SELECT SaleAnimal.AnimalID, Animal.Category, SaleAnimal.SalePrice
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE ((Animal.Category=‘Cat’) AND (SaleAnimal.SalePrice>
( SELECT AVG(SalePrice)
FROM Animal
INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE (Animal.Category=‘Cat’)
) ) );
Animal
SaleAnimal
AnimalID
Name
Category
Breed
SaleID
AnimalID
SalePrice
Field
AnimalID
Name
Category
SalePrice
Table
Animal
Animal
Animal
SaleAnimal
Sort
Criteria
 Don’t know the
average, so use a
subquery to look it up.
 Watch parentheses.
Descending
3
> (SELECT Avg(SalePrice) FROM Animal INNER
JOIN SaleAnimal ON Animal.AnimalID =
SaleAnimal.AnimalID WHERE Animal.Category =
‘Cat’)
Or
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Correlated Subquery
 List the Animals that have sold for a price higher than the
average for animals in that Category.
SELECT AnimalID, Name, Category, SalePrice
FROM Animal INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE (SaleAnimal.SalePrice>
(SELECT Avg(SaleAnimal.SalePrice)
FROM Animal INNER JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE (Animal.Category = Animal.Category) ) )
ORDER BY SaleAnimal.SalePrice DESC;
 The subquery needs to compute the average for a given
category.
 Problem: Which category?
 Answer: the category that matches the category from the main
part of the query.
 Problem: How do we refer to it? Both tables are called Animal.
This query will not work yet.
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Query04_19
Correlated SubQuery (Avoid)
 Match category in subquery with top level
 Rename tables (As)
 Correlated Subquery
 Recompute subquery for every row in top level--slow!
 Better to compute and save Subquery, then use in join.
SELECT A1.AnimalID, A1.Name, A1.Category, SaleAnimal.SalePrice
FROM Animal As A1 INNER JOIN SaleAnimal
ON A1.AnimalID = SaleAnimal.AnimalID
WHERE (SaleAnimal.SalePrice>
(SELECT Avg(SaleAnimal.SalePrice)
FROM Animal As A2 INNER JOIN SaleAnimal
ON A2.AnimalID = SaleAnimal.AnimalID
WHERE (A2.Category = A1.Category) ) )
ORDER BY SaleAnimal.SalePrice DESC;
List the Animals that have sold for a price higher than the
average for animals in that Category.
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Correlated Subquery Problem
Animal + SaleAnimal
Category
Fish
Dog
Fish
Cat
Cat
Dog
Fish
Dog
Dog
SalePrice
$10.80
$156.66
$19.80
$173.99
$251.59
$183.38
$1.80
$150.11
$148.47
Compute Avg: $37.78
Compute Avg: $174.20
Compute Avg: $37.78
Compute Avg: $169.73
Compute Avg: $169.73
Recompute average
for every row in the
main query!
 Assume small query
 100,000 rows
 5 categories of 20,000 rows
 100,000 * 20,000 = 1 billion rows to read!
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More Efficient Solution: 2 queries
Animal + SaleAnimal
Category
Fish
Dog
Fish
Cat
Cat
Dog
Fish
Dog
Dog
Saved Query
SalePrice
$10.80
$156.66
$19.80
$173.99
$251.59
$183.38
$1.80
$150.11
$148.47
Category AvgOfSalePrice
JOIN
Animal.Category =
Query1.Category
Bird
Cat
Dog
Fish
Mammal
Reptile
Spider
$176.57
$169.73
$174.20
$37.78
$80.72
$181.83
$118.16
 Compute the averages once and save query
 JOIN saved query to main query
 Two passes through table: 1 billion / 200,000 => 10,000
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UNION Operator
SELECT EID, Name, Phone, Salary, ‘East’ AS Office
FROM EmployeeEast
UNION
SELECT EID, Name, Phone, Salary, ‘West’ AS Office
FROM EmployeeWest




EID
352
876
372
Name
Jones
Inez
Stoiko
Phone
3352
8736
7632
Salary
45,000
47,000
38,000
Office
East
East
East
890
361
Smythe
Kim
9803
7736
62,000
73,000
West
West
Offices in Los Angeles and New York.
Each has an Employee table (East and West).
Need to search data from both tables.
Columns in the two SELECT lines must match.
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UNION, INTERSECT, EXCEPT
A
T1
B
List the name of any employee
who has worked for both the
East and West regions.
C
T2
T1 UNION T2
T1 INTERSECT T2
T1 EXCEPT T2
A+B+C
B
A
SELECT EID, Name
FROM EmployeeEast
INTERSECT
SELECT EID, Name
FROM EmployeeWest
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Multiple JOIN Columns
Breed
Category
Breed
Animal
AnimalID
Name
Category
Breed
DateBorn
Gender
...
SELECT *
FROM Breed INNER JOIN Animal
ON Breed.Category = Animal.Category
AND Breed.Breed = Animal.Breed
 Sometimes need to JOIN tables on more than one column.
 PetStore: Category and Breed.
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Reflexive Join
Employee
SQL
SELECT Employee.EID,
Employee.Name,
Employee.Manager, E2.Name
EID
115
462
523
765
Name
...
Sanchez
Miller
Hawk
Munoz
Manager
765
115
115
886
FROM Employee INNER JOIN
Employee AS E2
Result
ON Employee.Manager = E2.EID
EID
115
462
523
Name
Sanchez
Miller
Hawk
Manager
765
115
115
Name
Munoz
Sanchez
Sanchez
 Need to connect a table to itself.
 Common example: Employee(EID, Name, . . ., Manager)
 A manager is also an employee.
 Use a second copy of the table and an alias.
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Recursive Joins (SQL 99 and 200x)
WITH RECURSIVE EmployeeList (EmployeeID, Title, Salary) AS
( SELECT EmployeeID, Title, 0.00
FROM Manages WHERE Title = “CEO” -- starting level
UNION ALL
SELECT Manages.EmployeeID, Manages.Title, Manages.Salary
FROM EmployeeList INNER JOIN Manages
ON EmployeeList.EmployeeID = Manages.ManagerID )
SELECT EmployeeID, Count(Title), Sum(Salary)
FROM EmployeeList
GROUP BY EmployeEID ;
List all of the employees and list everyone who reports to them.
Not yet supported by vendors.
It provides tree spanning capabilities.
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Not available in Microsoft Access. It is in SQL Server and Oracle.
CASE Function
Select AnimalID,
CASE
WHEN Date()-DateBorn < 90 Then “Baby”
WHEN Date()-DateBorn >= 90
AND Date()-DateBorn < 270 Then “Young”
WHEN Date()-DateBorn >= 270
AND Date()-DateBorn < 365 Then “Grown”
ELSE “Experienced”
END
FROM Animal;
 Used to change data to a different context.
 Example: Define age categories for the animals.




Less than 3 months
Between 3 months and 9 months
Between 9 months and 1 year
Over 1 year
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Inequality Join
 AccountsReceivable
 Categorize by Days Late
 30, 90, 120+
 Three queries?
 New table for business rules
AR(TransactionID, CustomerID, Amount, DateDue)
LateCategory(Category, MinDays, MaxDays, Charge, …)
Month
Quarter
Overdue
30
90
120
90
120
9999
3%
5%
10%
SELECT *
FROM AR INNER JOIN LateCategory
ON ((Date() - AR.DateDue) >= LateCategory.MinDays)
AND ((Date() - AR.DateDue) < LateCategory.MaxDays)
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SQL SELECT
SELECT DISTINCT Table.Column {AS alias} , . . .
FROM Table/Query
INNER JOIN Table/Query ON T1.ColA = T2.ColB
WHERE (condition)
GROUP BY Column
HAVING (group condition)
ORDER BY Table.Column
{ Union second select }
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SQL Mnemonic
Someone
SELECT
From
FROM
Ireland
INNER JOIN
Will
WHERE
Grow
GROUP BY
Horseradish and
HAVING
Onions
ORDER BY
SQL is picky about
putting the
commands in the
proper sequence.
If you have to
memorize the
sequence, this
mnemonic may be
helpful.
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SQL Data Definition
 Create Schema Authorization dbName password
 Create Table TableName (Column Type, . . .)
 Alter Table Table {Add, Column, Constraint, Drop}
 Drop {Table Table | Index Index On table}
 Create Index IndexName ON Table (Column
{ASC|DESC})
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Syntax Examples
CREATE TABLE Customer
(CustomerID INTEGER NOT NULL,
LastName CHAR (10),
more columns
);
ALTER TABLE Customer
DROP COLUMN ZipCode;
ALTER TABLE Customer
ADD COLUMN CellPhone CHAR(15);
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Queries with “Every” Need EXISTS
List the employees who have sold animals from every category.
Bird
1. Reeves
2. Gibson
3. Reasoner
4. Hopkins
5. James
6. Eaton
7. Farris
8. Carpenter
9. O’Connor
10. Shields
11. Smith
x
x
x
Cat
x
x
x
Dog
x
x
x
x
Fish
x
x
Mammal
x
x
Reptile
x
x
Spider
x
x
By hand: List the employees and the categories. Go through the
SaleAnimal list and check off the animals they have sold.
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Query With EXISTS
List the Animal categories that have not been sold by an employee (#5).
SELECT Category
FROM Category
WHERE (Category <> "Other") And Category NOT IN
(SELECT Animal.Category
FROM Animal INNER JOIN (Sale INNER JOIN SaleAnimal
ON Sale.SaleID = SaleAnimal.SaleID)
ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE Sale.EmployeeID = 5)
If this query returns any rows, then the employee has not sold every animal.
So list all the employees for whom the above query returns no rows:
SELECT EmployeeID, LastName FROM Employee
WHERE NOT EXISTS
(above query slightly modified.)
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Query for Every
SELECT Employee.EmployeeID, Employee.LastName
FROM Employee
WHERE Not Exists
(SELECT Category
FROM Category
WHERE (Category <> "Other") And Category NOT IN
(SELECT Animal.Category
FROM Animal INNER JOIN (Sale INNER JOIN SaleAnimal
ON Sale.SaleID = SaleAnimal.SaleID)
ON Animal.AnimalID = SaleAnimal.AnimalID
WHERE Sale.EmployeeID = Employee.EmployeeID)
);
Result:
3
Reasoner
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Simpler Query for Every
Sometimes it is easier to use Crosstab and the Count function.
EID
1
2
3
4
5
6
7
8
9
10
LastName Bird Cat Dog Fish Mammal Reptile Spider
Reeves
7
Gibson
2
6
12
2
1
2
Reasoner
3
6
14
2
1
1
1
Hopkins
2
4
14
1
James
3
8
7
5
1
2
Eaton
1
5
6
1
Farris
1
6
16
2
Carpenter
2
6
10
2
1
O'Connor
6
8
3
1
Shields
1
2
But some systems do not have Crosstab, and sometimes the
lists would be too long. So you need to know both techniques.
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SQL: Foreign Key
CREATE TABLE Order
(OrderID INTEGER NOT NULL,
OrderDate DATE,
CustomerID INTEGER
CONSTRAINT pkorder PRIMARY KEY (OrderID),
CONSTRAINT fkorder FOREIGN KEY (CustomerID)
REFERENCES Customer (CustomerID)
);
Order
OrderID
OrderDate
CustomerID
Customer
*
CustomerID
LastName
FirstName
Address
…
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SQL Data Manipulation Commands
Insert Into target (column1 . . .) VALUES (value1 . . .)
Insert Into target (column1 . . .) SELECT . . . FROM. . .
Delete From table WHERE condition
Update table SET Column=Value,. . . Where condition
Note the use of the Select and Where conditions.
Synatx is the same--only learn it once.
You can also use subqueries.
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Copy Old Animal Data
INSERT INTO OldAnimals
SELECT *
FROM Animal
WHERE AnimalID IN
(SELECT AnimalOrderItem.AnimalID
FROM AnimalOrder INNER JOIN AnimalOrderItem
ON AnimalOrder.OrderID = AnimalOrderItem.OrderID
WHERE (AnimalOrder.OrderDate<’01-Jan-2004’) );
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Delete Old Animal Data
DELETE
FROM Animal
WHERE AnimalID IN
(SELECT AnimalOrderItem.AnimalID
FROM AnimalOrder INNER JOIN AnimalOrderItem
ON AnimalOrder.OrderID = AnimalOrderItem.OrderID
WHERE (AnimalOrder.OrderDate<’01-Jan-2004’) );
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Update Example
UPDATE Animal
SET ListPrice = ListPrice*1.10
WHERE Category = ‘Cat’ ;
UPDATE Animal
SET ListPrice = ListPrice*1.20
WHERE Category = ‘Dog’ ;
 Change the ListPrice of Animals at the PetStore.
 For cats, increase the ListPrice by 10%.
 For dogs, increase the ListPrice by 20%.
 Typically use two similar UPDATE statements.
 With the CASE function, the statements can be combined.
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Quality: Building Queries
 Break questions into smaller pieces.
 Test each query.
Which customers who bought Dogs
 Check the SQL.
also bought products for Cats
 Look at the data.
(at any time)?
 Check computations
 Combine into subqueries.
 Use cut-and-paste to avoid errors.
 Check for correlated subqueries.
 Test sample data.
Who bought dogs?
Who bought cat products?
 Identify different cases.
 Check final query and subqueries.
 Verify calculations.
Dogs and cat products on the same sale.
Dogs and cat products at different times.
 Test SELECT queries
Dogs and never any cat products.
before executing
Cat products and never any Dogs.
UPDATE queries.
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Quality Queries: Example
Which customers who bought Dogs also bought products for Cats?
A. Which customers bought dogs?
B. Which customers bought cat products?
SELECT DISTINCT Animal.Category, Sale.CustomerID
FROM Sale INNER JOIN (Animal INNER JOIN SaleAnimal
ON Animal.AnimalID = SaleAnimal.AnimalID)
ON Sale.SaleID = SaleAnimal.SaleID
WHERE (((Animal.Category)=‘Dog’))
AND Sale.CustomerID IN (
SELECT DISTINCT Sale.CustomerID
FROM Sale INNER JOIN (Merchandise INNER JOIN SaleItem
ON Merchandise.ItemID = SaleItem.ItemID)
ON Sale.SaleID = SaleItem.SaleID
WHERE (((Merchandise.Category)=‘Cat’))
);
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Programming Review: Variables
 Integer
 2 bytes
 -32768 32767
 Long
 4 bytes
 +/- 2,147,483,648
 Single
 4 bytes
 +/- 3.402823 E 38
 +/- 1.401298 E-45
 Global, Const, Static
 Double
 8 bytes
 +/- 1.79769313486232 E 308
 +/- 4.94065645841247 E-324
 Currency
 8 bytes
 +/- 922,337,203,685,477.5808
 String & String*n
 Variant
 Any data type
 Null
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Programming: Scope and Lifetime
 Scope
 Where is the variable, and
which procedures can
access it?
Form
Button1
Button2
 Lifetime
 When is the variable
created, and when is it
destroyed?
Different procedures,
different variables.
Created and destroyed
each time the button
is clicked.
Form--Module Code
Sub Button1_Click()
Dim i1 As Integer
i1 = 3
End Sub
Sub Button2_Click()
Dim i1 As Integer
i1 = 7
End Sub
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Programming: Global Variables
 Wider scope and lifetime
 Created at a higher level
 Form
 Public module
 Accessible to any procedure
in that form or module.
 Declare it Global to make it
available to any procedure.
Form
Button1
Button2
Form--Module Code
Dim i2 As Integer
Sub Button1_Click()
i2 = 20
End Sub
Variable is created when
form is opened.
Sub Button2_Click()
Clicking Button1 sets the
i2 = i2 + 7
initial value.
End Sub
Clicking Button2 modifies
the value.
What if user clicks buttons in a different order?
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Programming: Computations
 Standard Math
+ - * /
 \ Integer divide
 ^ Exponentiation
 (2^3 = 2*2*2 = 8)
 Mod
 (15 Mod 4 = 3) (12 + 3 = 15)
“Frank” & “Rose”  “FrankRose”
Left(“Jackson”,5)  “Jacks”
Trim(“
Maria “)  “Maria”
 String










& Concatenation
Left, Right, Mid
Trim, LTrim, RTrim
String
Chr, Asc
LCase, UCase
InStr
Len
StrComp
Format
Len(“Ramanujan”)  9
String(5,”a”)  “aaaaa”
InStr(“8764 Main”,” “)  5
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Programming: Standard Functions
 Numeric







Exp, Log
Atn, Cos, Sin, Tan
Sqr
Abs
Sgn
Int, Fix
Rnd, Randomize
=30
x = loge
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Trigonometric functions
(ex)
?
2 = 1.414
Abs(-35)  35
Sgn(-35)  -1
Int(17.893)  17
Rnd()  0.198474
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Programming:
Standard Functions: Date/Time
 Date, Now, Time
 DateAdd, DateDiff




“y”, “m”, “q” . . .
Firstweekday
1=Sunday,. . .
Can also be used
to find number of
Fridays, between
two dates.
02/19/04
today
03/21/04
DateDue
DateDue = DateAdd(“d”, 30, Date())
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Programming:
Standard Functions: Variant
 Variant





IsDate
IsNumeric
VarType
IsEmpty
IsNull
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Programming: Debug






Stop
Ctrl-Break
F5: Go
F8: Step through
S-F8: Step over
Breakpoints
 Immediate Window
 ? or Print
 Any assignment
 Any code
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 MsgBox
Programming:
Output: Message Box
 Message
 Type
 Title
 Types: Use Constants




vbOKOnly vbOKCancel
vbAbortRetryIgnore
vbYesNoCancel
vbYesNo vbRetryCancel
 Defaults
 vbDefaultButton1
 vbDefaultButton2
 vbDefaultButton3
 Icons




vbCritical Stop sign
vbQuestion Question mark
vbExclamation Warning
vbInformation Circle i
 Responses




vbOK
vbCancel
vbAbort vbRetry
vbIgnore
vbYes
vbNo
MsgBox "This is a message box", vbYesNoCancel + vbInformation, "Sample Box"
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 InputBox




Programming:
Input: InputBox
Prompt
Title
Default
X-Pos, Y-Pos
 Prompt
 Cannot change box size
 Use Chr(10) & Chr(13) for
blank lines.
 Returns text or Variant
 Cancel = zero string ““
 Positions




Twips
Twentieth of inch point
72 points
1440 twips per inch
Dim str As String
str = InputBox(
"Enter your name:",
"Sample Input", ,
5000, 5000)
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Programming: Conditions
 If
 Conditions
 If (Condition) Then
 statements for true
 Else
 <, <=, >, >=, =, <>
 And, Or, Not, Xor
 Eqv, Imp (logic)
 statements for false
 End If
 IIF (Cond., True, False)
 Select Case (expr)
 Case value
 statements
 Case value2
 Case Else
 End Select
If (Condition1) Then
statements for true
Else
statements for false
If (Condition2) Then
statements for true
End If
End If
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Programming
Select Example
 Message Box
 Could use repeated If
statements
 Better to use Select Case
response = MsgBox(…)
If (response == vbYes) Then
‘ statements for Yes
Else
If (response == vbNo) Then
‘ statements for No
Else
‘statements for Cancel
End If
End If
response = MsgBox(…)
Select Case response
Case vbYes
‘ statements for Yes
Case vbNo
‘ statements for No
Case vbCancel
‘ statements for Cancel
End Case
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Programming: Loops
Initialize value
Statements
 Do
 For … Next
 For Each
Change value
Test condition
Do Until (x > 10)
Do While (x <= 10)
‘ Statements
‘ Statements
x=x+1
x=x+1
Loop
Loop
Do
For x = 1 to 10
‘ Statements
x=x+1
‘ Statements
Next x
Loop Until (x > 10)
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Programming: Loops Again
 Do
 For/Each (objects)
 Do {While | Until}
 Exit Do (optional)
 Loop
 For Each element In group
 [Exit For] (optional)
 Next element
 With (objects)
 Do
 Loop {While | Until}
 With object
 End With
 For/Next
 For counter = start To end
Step increment
 Exit For (optional)
 Next counter
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Programming
Subroutines and Functions
 Sub name (var1 As . . ., var2, . . .)
 End Sub
 Function fname (var1 As . . .) As datatype
 fname = …
‘ returns a specific value
 End Function
 Variables are passed by reference
 Changes made to the parameters in the subroutine are passed
back to the caller.
 Unless you use ByVal
 Changes are made to a copy of the parameter, but are not
returned to the calling program.
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Programming: Example Subroutine
Main program
…
StatusMessage “Trying to connect.”
…
StatusMessage “Verifying access.”
…
End main program
Sub StatusMessage (Msg As String)
‘ Display Msg, location, color
End Sub
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Programming: Parameter Types
Main
j=3
DoSum j
… ‘ j is now equal to 8
Subroutine DoSum (j2 As Integer)
j2 = 8
End Sub
Main
j=3
DoSum j
… ‘ j is still equal to 3
Subroutine DoSum (ByVal j2 As Integer)
j2 = 8
End Sub
By Reference
Changes to data in the
subroutine are passed back.
By Value
Creates a copy of the
variable, so changes are
not returned.
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Programming
Arrays and User Types
 Arrays
 Dim array(sub, . . .) As
type
 Dim iSorts(10) As Integer
 Specifying bounds:
 (lower To upper, . . .)
 ReDim [Preserve] array ..
.
 Option Base 0 | 1
 v 2.0 arrays less than
64KB
 User defined types
 Type Tname
ename1 As type
ename2 As type
 End Type
 Dim var1 As Tname
 var1.ename1 = . . .
 var1.ename2 = . . .
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Programming: Financial Functions
 Fixed payments
 PV (rate, nper, pmt, fv, due)
 FV (rate, nper, pmt, pv, due)
 IPmt (rate, per, nper, pv, fv,
due)
 NPer (rate, pmt, pv, fv, due)
 Pmt (rate, nper, pv, fv,due)
 PPmt (rate, per, nper, pv, fv,
due)
 Rate (nper, pmt, pv, fv, due,
guess)






rate
per
nper
pv
fv
due
 Arrays
 NPV (rate, array)
 IRR (array, guess)
 MIRR (array, finrate, re_rate)
 Depreciation
 DDB (cost, salv, life, period)
 SLN (cost, salvage, life)
 SYD (cost, salv., life, period)
interest rate per period
specific period number
# of periods
present value
future value
0=due at end, 1=due at start
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Programming: Text File Input/Output







Open filename As # file#
Close # file#, Reset
Print #,Put, Write
Spc, Tab
Get, Input #, Line Input #
EOF, LOF
Seek # file#, position





ChDir, ChDirve
Dir
Kill, (re)Name
Lock, Unlock
CurDir, MkDir, RmDir
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OLE: Object Linking & Embedding
 CreateObject (class)
 “appname . objecttype”
 GetObject (file, class)
 Methods and syntax are
defined by the software that
exports the object.
 Example
 Dim obj As Object
 set obj =
CreateObject(“Word.Basic”)
 obj.Bold
 obj.Insert “text”
 obj.SaveAs “file”
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DDE: Dynamic Data Exchange




Shell
DDEInitiate
DDEExecute
DDEPoke, DDE Send




Application must be running
Start a conversation/topic
Issue a command
Place data
 Send data
 DDE, DDERequest
 Get data
 Request data
 DDETerminate
 Close the session
63
Database Management Systems
End of
Chapter 5
McGraw-Hill/Irwin
Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.