Chapter 5

Advanced Querying

1

Based on G. Post, DBMS: Designing & Building Business Applications

University of ManitobaAsper School of Business

3500 DBMSBob Travica

Updated 2015

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Use of Advanced Queries

Harder questions calling for joining tables Subqueries In, Not In clauses INNER JOIN, LEFT JOIN, RIGHT JOIN UNION, INTERSECT & other support to Boolean

logic, CASE

Download Sally’s Pet Store 2010 (queries work with it)

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Harder Questions

11) List last names of customers who bought something between 4/1/2010 and 5/31/2010.

12) List the Last Name and Phone of anyone who bought a registered white cat between 6/1/1998 and 12/31/2010.

13) How many cats are “in-stock” on 10/1/2010?

14) Which cats sold for more than the average price of cats?

15) Which animals sold for more than the average price of animals in their category?

16) Which animals have not been sold?

17) Which animals have been sold?

17) Which customers (who bought something at least once) did not buy anything between 11/1/2010 and 12/31/2010?

18) Which customers who bought dogs also bought products for cats (at any time)?

(Numbering continues from last lecture)

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SupplierIDNameContactNamePhoneAddressZipCodeCityID

Supplier

PONumberOrderDateReceiveDateSupplierIDEmployeeIDShippingCost

MerchandiseOrder

OrderIDOrderDateReceiveDateSupplierIDShippingCostEmployeeID

AnimalOrder

OrderIDAnimalIDCost

AnimalOrderItem

CityIDZipCodeCityStateAreaCodePopulation1990Population1980CountryLatitudeLongitude

City

EmployeeIDLastNameFirstNamePhoneAddressZipCodeCityIDTaxPayerIDDateHiredDateReleased

Employee

PONumberItemIDQuantityCost

OrderItem

CategoryRegistration

Category

CategoryBreed

Breed

AnimalIDNameCategoryBreedDateBornGenderRegisteredColorListPricePhoto

Animal

SaleIDSaleDateEmployeeIDCustomerIDSalesTax

Sale

SaleIDItemIDQuantitySalePrice

SaleItem

ItemIDDescriptionQuantityOnHandListPriceCategory

Merchandise

SaleIDAnimalIDSalePrice

SaleAnimal

CustomerIDPhoneFirstNameLastNameAddressZipCodeCityID

Customer

*

*

*

*

*

*

*

*

*

**

*

*

*

**

*

**

*

Know your data! Sally’s Pet Store Schema(2007 version)

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Joining Two Tables Query #11: List LastNames of Customers who bought something

between 4/1/2010 and 5/31/2010.

SELECT DISTINCT Sale.CustomerID, Customer.LastNameFROM CustomerINNER JOIN Sale ON Customer.CustomerID = Sale.CustomerIDWHERE Sale.SaleDate BETWEEN #4/1/2010# AND #5/31/2010#ORDER BY Customer.LastName;

Output:20 rows

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SQL Inner Join Syntax

SELECT column(s)

FROM table1

INNER JOIN table2 ON table1.columnA = table2.columnA

WHERE constraints

• Inner Join is most frequently used

• Matches rows from different tables based on

matching values of PKs and FKs

Primary Key Foreign Key

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Joining More than Two Tables

Query #12: List the Last Name and Phone of customers who bought a registered white cat between 6/1/2010 and 12/31/2010.

SELECT Customer.LastName, Customer.Phone, Animal.Category, Animal.Color, Animal.Registered, Sale.SaleDateFROM CustomerINNER JOIN (Sale INNER JOIN Animal ON Sale.SaleID=Animal.SaleID) ON Customer.CustomerID=Sale.CustomerIDWHERE Animal.Category="Cat" AND Animal.Color LIKE "*White*" AND Animal.Registered IS NOT Null AND Sale.SaleDate Between #6/1/2010# And #12/31/2010# ;

See Footnote!

Output: 4 rowsLastName Phone Category Color Registered SaleDate

Bell (717) 244-3484 Cat White CFA 22/12/2010

Kidd (207) 585-7583 Cat White CFA 09/12/2010

Hooks (618) 109-9250 Cat White/Black CFA 03/12/2010

Hinton (606) 241-3182 Cat White CFA 16/08/2010

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SELECT Customer.LastName, Customer.Phone, Animal.Category, Animal.Color, Animal.Registered, Sale.SaleDate

FROM Customer, Sale, Animal

WHERE Sale.SaleID=Animal.SaleID

AND Customer.CustomerID=Sale.CustomerID

AND

Animal.Category="Cat" AND Animal.Color LIKE "*White*" AND Animal.Registered IS NOT Null AND Sale.SaleDate Between #6/1/2010# And #12/31/2010# ;

Query #16 simplified -To avoid complications with parentheses, you can write the same query by suing an older SQL statement: the WHERE line both joins the tables and sets the constraints.

Disadvantages: the mix-up in the WHERE line (FKs/PKs and constraints).

Still may save time for query writing.

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Building a Query Query #12: List the Last Name and Phone of anyone who bought a

registered white cat between 6/1/2010 and 12/31/2010.

Identify the tables involved. Look at the columns you want to see.

LastName, Phone: Customer

Look at the columns used in the constraints. Registered, Color, Category: Animal SaleDate: Sale

Find linking tables. To link Animal with Sale: SaleAnimal

Select the desired columns (may be computed as well) and test the query.

Enter the constraints.

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SQL Mnemonic (Remember!)

Someone

From

Ireland (Italy, India…)

Will

Grow

Horseradish &

Onions

SELECT

FROM

INNER JOIN

WHERE

GROUP BY

HAVING

ORDER BY

SQL is picky about putting the commands in the proper sequence.

For memorizing the sequence, use this mnemonic.

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Levels of automation: Sub-query 1/2

Query #14: List the cats that drew a donation bigger than the average.

SELECT Animal.AnimalID, Animal.Category, Animal.Breed, Animal.DonationFROM AnimalWHERE (Animal.Category="Cat") AND (Animal.Donation>171.82);

SELECT Category, AVG(Donation) As [Average Donation] FROM Animal WHERE Category="Cat“ ;

We can find the answer in 2 steps:1. Find what the average price for cats is ($171.82).

2. Use the average price as a constraint in another query:

See Note…

Output:

Category Average Donation

Cat $171.82

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Levels of automation: Sub-query 2/2

A more automated solution that executes in 1 step. Uses query 2 on top and query 1 in the sub-query.

SELECT Animal.AnimalID, Animal.Category, Animal.Breed, Animal.Donation

FROM Animal

WHERE ((

(Animal.Category="Cat") AND ((Animal.Donation >

(SELECT AVG(Donation)

FROM Animal

WHERE Animal.Category="Cat"))

)))

ORDER BY Animal.Donation;

Output: 23 rows

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Querying Set of Rows with operator IN Query: List names of customers who purchased one of the following

items: 1, 2, 30, 32, 33.

SELECT Customer.LastName, Customer.FirstName, SaleItem.ItemIDFROM (Customer INNER JOIN Sale ON Customer.CustomerID = Sale.CustomerID) INNER JOIN SaleItem ON Sale.SaleID = SaleItem.SaleIDWHERE SaleItem.ItemID In (1,2,30,32,33)ORDER BY Customer.LastName, Customer.FirstName;

Output: 39 rows

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Using IN with a Sub-query Query: List all customers who bought items for cats.

SELECT Customer.CustomerID, Customer.LastName, Customer.FirstName, SaleItem.ItemIDFROM

(Customer INNER JOIN Sale ON Customer.CustomerID = Sale.CustomerID)INNER JOIN SaleItem ON Sale.SaleID = SaleItem.SaleID

WHERE (SaleItem.ItemID In(SELECT Merchandise.ItemID FROM Merchandise WHERE Category="Cat") )

ORDER BY Customer.LastName Asc;

Note: 3 tables joined and 4 tables used. Output: 79 rows.

• An alternative simplified using older SQL syntax and 4 tables to show description of merchandise:

SELECT Customer.CustomerID, Customer.LastName, Customer.FirstName, SaleItem.ItemID, Merchandise.Description

FROM Customer, Sale, SaleItem, Merchandise

WHERE (Customer.CustomerID = Sale.CustomerID) AND (Sale.SaleID = SaleItem.SaleID) AND (SaleItem.ItemID = Merchandise.ItemID) AND (Merchandise.Category="Cat")

ORDER BY Customer.LastName Asc;

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SubQuery: NOT IN (Subtract)

Query #16: Which animals have not been sold (adopted)? Start with list of all animals. Select those whose IDs are not is sales records.

SELECT Animal.AnimalID, Animal.Name, Animal.Category, Animal.SaleID

FROM Animal

WHERE Animal.AnimalID NOT IN (SELECT AnimalID FROM Animal INNER JOIN Sale ON Animal.SaleID=Sale.SaleID);

Output: 10 rowsAnimalID Name Category SaleID

2 Fish

4 Simon Dog

12 Leisha Dog

19 Gene Dog

25 Vivian Dog

34 Rhonda Dog

88 Brandy Dog

175 Donald Cat

181 Fish

201 Mammal

See Note for optional query.

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SQL Mnemonic (again)

Someone - SELECT

From - FROM

Ireland - INNER JOIN

Will - WHERE

Grow - GROUP BY

Horseradish & - HAVING

Onions - ORDER BY

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Outer Join: Left Outer Join

Query #16: “Which animals have not been sold?” with LEFT JOIN Output building:

SELECT *FROM Animal LEFT JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalID;

LEFT JOIN creates a transient table with:

All rows from left table Animal pasted with matching rows in SaleAnimal

Blank attributes (null values) in SaleAnimal for the rows in Animal that were not macthed.**

SELECT Animal.AnimalID, Animal.Name, Animal.CategoryFROM Animal LEFT JOIN SaleAnimal ON Animal.AnimalID = SaleAnimal.AnimalIDWHERE (SaleAnimal.AnimalID Is Null);

To get just the non-matched rows, add the WHERE line:

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Query #17: Which animals have been sold?

Outer Join: Right Outer Join

SELECT Animal.AnimalID, Animal.Name, Animal.Category

FROM Animal RIGHT JOIN SaleAnimal

ON Animal.AnimalID = SaleAnimal.AnimalID;

Actually, in this case equivalent to:

SELECT Animal.AnimalID, Name, Category

FROM SaleAnimal INNER JOIN Animal

ON SaleAnimal.AnimalID=Animal.AnimalID;

… because RIGHT JOIN selects all the records from the right table(SaleAnimal) and matching records from the left table (Animal).There can be no blank fields, because Animal provides FK for SaleAnimal—all AnimalIDs in SaleAnimal are matched in Animal.

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Types of Join - Summary

Inner Join + =

Left Join +

+

=

Right Join =

Note: RIGHT JOIN can be presented as LEFT JOIN by reversingorder of tables.

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UNION Operator

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.

SELECT EID, Name, Phone, Salary, ‘East’ AS OfficeFROM EmployeeEastUNIONSELECT EID, Name, Phone, Salary, ‘West’ AS OfficeFROM EmployeeWest

EID Name Phone Salary Office352 Jones 3352 45,000 East876 Inez 8736 47,000 East372 Stoiko 7632 38,000 East

890 Smythe 9803 62,000 West361 Kim 7736 73,000 West

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UNION, INTERSECT, EXCEPT(Boolean Logic)

T1 T2

A AC CSELECT EID, NameFROM EmployeeEastINTERSECTSELECT EID, NameFROM EmployeeWest

List the name of any employee who has worked for both the East and West regions:

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CASE Function

Used for grouping objects, complex decisions. 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

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”

ENDFROM Animal;

( SQL Server, Oracle)