CS&E 1111 AcInnerJoins Inner Joins Objectives: Creating Queries with data from Multiple Tables Joining two tables using an Inner Join Referential Data

CS&E 1111 AcInnerJoins

Inner JoinsInner Joins

Objectives: Creating Queries with data from Multiple Tables• Joining two tables using an Inner Join • Referential Data Integrity

•Cascade Update & Cascade Delete• Joining three tables

•Table with a Many-One-Many relationship•Tables with a One-Many-One

relationship


Let’s look at a database with 3 tables:Let’s look at a database with 3 tables: What are the primary keys in these tables? What are the foreign key relationships we can setup?

18

81

* Primary Keys

Fruits Fruitid Priceapples 1 1.29$ pears 2 2.45$ bananas 3 0.15$ grapes 4 1.89$

FruitidQty Shipped

4 23 44 31 27 11 3

FruitidQty Received

1 31 43 65 5

FruitidQty Received

Received

FruitidFruitPrice

FruitListFruitidQty Shipped

Shipped

FruitList Received Shipped


Using Multiple Tables in a QueryUsing Multiple Tables in a QueryQueries become much more powerful when you can combine information from 2 or more tables. We can combine the records in the two tables using an inner join operation using the following steps:

Add both tables to the query design view

Setup the appropriate relationships if they have not been done so on the relationship table.

Choose the appropriate fields, criteria, sort, etc.

Run your query and look at the results


Create a list of Fruit, by name/id and the quantity shipped.Create a list of Fruit, by name/id and the quantity shipped.

What does the resulting dynaset look like?

8

1Fruitid

FruitPrice

FruitListFruitidQty Shipped

Shipped

FIELD Fruit Fruitid Qty ShippedTABLE Fruitlist Fruitlist ShippedTOTALSORTSHOWCRITERIAOROR


The “inner join” results in a list of only records which have a matching record on the related table

The “inner join” results in a list of only records which have a matching record on the related table

Fruits Fruitidapples 1 pears 2 bananas 3 grapes 4

Fruits FruitidQty Shipped

apples 1 2apples 1 3bananas 3 4grapes 4 3grapes 4 2

Joined of FruitID

What happened to the shipment for fruitID 7?

What happened to pears (id #2) on the resulting list?Shipped

Fruitlist

FruitidQty Shipped

4 23 44 31 27 11 3


•The computer generates a master list of all combinations of the two sets of data

•When you join on a specific field (foreign key), using an inner join, it will select only those combinations that contain a matching value in the join fields.

To understand why we only get records with “matching” foreign key fields, we need to

understand how the computer creates an Inner Join


The “master list”The “master list”

+

The resulting list will have 4 x 6 or 24 possible combinations. But ONLY combinations with matching FruitID’s provide relevant information and are included in the inner join record set.

ShippedFruitlistFruits Fruitidapples 1 pears 2 bananas 3 grapes 4

FruitidQty Shipped

4 23 44 31 27 11 3

fruitsfruitlist.fruitid

fruitship.fruitid

qty shipped

apples 1 4 2pears 2 4 2bananas 3 4 2grapes 4 4 2apples 1 3 4pears 2 3 4bananas 3 3 4grapes 4 3 4apples 1 4 3pears 2 4 3bananas 3 4 3grapes 4 4 3apples 1 1 2pears 2 1 2bananas 3 1 2grapes 4 1 2apples 1 7 1pears 2 7 1bananas 3 7 1grapes 4 7 1apples 1 1 3pears 2 1 3bananas 3 1 3grapes 4 1 3

The 1st combo - the Fruitid’s do not match thus it will not be included in the record set


The combined record set formed from an Inner Join

The combined record set formed from an Inner Join

Since pears do not appear on the Shipped table it does not appear on the joined list. Similarly there is no FruitID 7 on the Fruitlist so it too will not be included on the joined list.

Shipped

FruitlistFruits Fruitidapples 1 pears 2 bananas 3 grapes 4



FruitidQty Shipped

4 23 44 31 27 11 3


Now summarize this list by fruit – using the Aggregate function sum

Now summarize this list by fruit – using the Aggregate function sum

Available records

The resulting dynaset:



FIELD Fruit Fruidid Qty ShippedTABLE Fruitlist Fruistlist ShippedTOTAL Group by Group by SumSORTSHOW x x xCRITERIA

Fruits FruitidSum of Quantity Shipped

apples 1 5bananas 3 4grapes 4 5


Do we want to be able to ship a fruit (fruitid 7) that we don’t have listed on the Fruit table?

We can control whether or not this situation can occur by editing our relationship properties.

Shipped

FruitlistFruits Fruitidapples 1 pears 2 bananas 3 grapes 4



FruitidQty Shipped

4 23 44 31 27 11 3


Referential Data IntegrityReferential Data Integrity

In Access you can choose to limit entries made in a foreign key field to those items listed in the primary key field of the related table. This is known as enforcing Referential Data Integrity.

Is Referential Data Integrity violated here?

81

Fruitlist Received

Fruits Fruitid Priceapples 1 1.29$ pears 2 2.45$ bananas 3 0.15$ grapes 4 1.89$

FruitidQty Received

1 31 43 65 5


Cascade Update Related FieldsCascade Update Related FieldsWhat happens when you change a FruitID?In Access, if Referential Data integrity is enforced, you can specify whether or not to Cascade Update Related records such that changing any entry in a primary key field will automatically change the entries in foreign key fields of related tables.

If you change bananas to ID 9 and use this property –

the related record on the shipped table will

be updated Shipped

FruitListFruits Fruitidapples 1 pears 2 bananas 3 grapes 4

FruitidQty Shipped

4 23 44 31 27 11 3

9

9


Cascade Delete Related FieldsCascade Delete Related FieldsWhat happens when you change a FruitID?

In Access, if Referential Data integrity is enforced, you can specify whether or not to Cascade Delete Related records such that removing any entry in a primary key field will automatically remove all entries in foreign key fields of related tables.

If you delete bananas’ ID 3 all

records for ID3 in the payment table will be

deleted

Shipped

Fruitlist Fruits Fruitidapples 1 pears 2 bananas 3 grapes 4

FruitidQty Shipped

4 23 44 31 27 11 3


Given the above tables:•Is data integrity enforced for each relationship?•What would happen if I deleted grapes from the

Fruitlist?•What would happen if I changed the Fruitid of

grapes to 6?

Received Shipped

FruitidQty Received

1 31 43 64 2

FruitidQty Shipped

4 23 44 31 27 11 3

Fruitlist



These rules are specified from the Relationships table – Edit Relationships

These rules are specified from the Relationships table – Edit Relationships


Much like a manual process - if a piece of data cannot be uniquely associated with a corresponding value – it may not be possible to “join” them (many-many relationship).

Consider some of the possible relationship scenarios (∞-1- ∞,1-∞-1) and explore how Access will join tables with these types of relationships.

Can we join more than 2 tables at a time?Can we join more than 2 tables at a time?


Joining More than Two Tableswith a many-one-many relationship

Joining More than Two Tableswith a many-one-many relationship

Here each fruit may have multiple shipments and multiple receipts. Therefore there is a many-to-many relationship between the records on the Orders table and the records on the Payments table.

18 81

FruitidQty Received

1 31 43 65 5

FruitidQty Shipped

4 23 44 31 27 11 3


Receive FruitListShipped


Joining More than Two Tables Joining More than Two Tables How does Access combine more than two tables? First it combines just two tables in the same manner we’ve seen before to create the combined record set.

Shipped

FruitList

FruitidQty Shipped

4 23 44 31 27 11 3


fruitship.fruitid

qty shipped

apples 1 1 2apples 1 1 3bananas 3 3 4grapes 4 4 3grapes 4 4 2



Joining More than Two Tables Joining More than Two Tables Next Access takes this combined record set and joins

it by FruitId to the Received table

Since the joins are all on the same foreign key field - the combined record set contains only those records where the join fields match in all three fruitid fields

ReceivedCombinedRecord Set

FruitidQty Received

1 31 43 65 5

fruitsfruitlist.f

ruitidfruitship.fruitid

qty shipped

receipts.fruitid

qty received

apples 1 1 2 1 3apples 1 1 3 1 3apples 1 1 2 1 4apples 1 1 3 1 4bananas 3 3 4 3 6


fruitship.fruitid

qty shipped

apples 1 1 2apples 1 1 3bananas 3 3 4grapes 4 4 3grapes 4 4 2


Only matching records from all 3 tables are selected. So if grapes have no receipts, even if it has shipments

it will not appear in the query result For records with both shipments and receipts the

computer looks at every possible combination Apples with two shipments and two receipts results in

4 joins – Is this correct?

This results in the following Record Set:This results in the following Record Set:

fruits fruitidqty

receivedqty

shippedapples 1 3 2apples 1 3 3apples 1 4 2apples 1 4 3bananas 3 6 4


Are the resulting values correct? Are the resulting values correct?

Group by

Directly joining all three tables that have a many-one-many relationship results in incorrect values

Apples has shipped 5 and received of 7 not the values

shown

FruitidQty Received

1 31 43 65 5

FruitidQty Shipped

4 23 44 31 27 11 3


ReceivedFruitist

Shipped

18 81

fruitsfruiti

dSumOfqty received

SumOfqty shipped

apples 1 14 10bananas 3 6 4

fruits fruitidqty

receivedqty

shippedapples 1 3 2apples 1 3 3apples 1 4 2apples 1 4 3bananas 3 6 4


Can these three tables be directly joined to give us a valid record set ?

Can these three tables be directly joined to give us a valid record set ?

Does each received listing (many) correspond to a single vendor (one) and a single fruit (one)? If so – then this 3-way join is valid.

Notice the Vendor field has been added to the Received table and

related to a Vendors table

Fruits Name Fruitid

apples 1 pears 2 bananas 3 grapes 4

FruitidQty Received Vendor

1 3 21 4 33 6 14 5 2

Vendor Company Name1 Washington Co.2 ABC Importers3 Florida Grows4 California Inc

ReceivedFruitlistVendors

8 81 1


Here is the record set resulting from Joining all 3 tables having a One-Many-One Relationship

Here is the record set resulting from Joining all 3 tables having a One-Many-One Relationship

Is this a valid record set – are items missing that should be included, are items duplicated?

Fruits NameFruitlist.Fruidid Fruitid

Qty Received

Received.Vendor

Vendors.Vendor Company Name

apples 1 1 3 2 2 ABC Importersapples 1 1 4 3 3 Florida Growsbananas 3 3 6 1 1 Washington Co.grapes 4 4 5 2 2 ABC Importers


1 3 21 4 33 6 14 5 2

Fruitlist & Received joined on Fruitid

Combined records joined by Vendor


In a One-Many-One relationship, a three-way join does result in a valid record set.In a One-Many-One relationship, a three-way join does result in a valid record set.

• What happened to fruitid 2 (pears) or vendor 4 (California Inc)?

Fruits Name Fruitid

apples 1 pears 2 bananas 3 grapes 4


1 3 21 4 33 6 14 5 2

Vendor Company Name1 Washington Co.2 ABC Importers3 Florida Grows4 California Inc

Received FruitlistVendors

8 81 1

Company Name Fruits Name

Qty Received

ABC Importers apples 3Florida Grows apples 4Washington Co. bananas 6ABC Importers grapes 5


Can We Join More than Two Tables With Other Relationship Combinations?

Can We Join More than Two Tables With Other Relationship Combinations?

Fruits Name Fruitid type

apples 1 Apears 2 Abananas 3 Bgrapes 4 C


1 3 21 4 33 6 14 5 2

Received Fruitlist

8 1type origin

A domesticB BrazilC Chile

18

If a single record on the “many” side can be related to a single unique record on the other tables we combine these 3 tables to get a valid record set.

One can combine 3 or more tables into valid record sets as long as there are no “many” to “many” relationships resulting

directly or indirectly from these joins

Type


Valid record sets from joins of 3 or more tables can be created as long as there are no

many to many (∞-1-∞) relationships

Valid record sets from joins of 3 or more tables can be created as long as there are no

many to many (∞-1-∞) relationships

Fruits Name Fruitid type

apples 1 Apears 2 Abananas 3 Bgrapes 4 C


1 3 21 4 33 6 14 5 2

Received

Fruitlist8

1

type origin

A domesticB BrazilC Chile

1

8

Type


Joining Tables - Recap:Joining Tables - Recap:

Inner Join of two tables (or queries) Join on a valid foreign key field - (one-one, one-

many) Record set contains only records in common

Referential Data Integrity Can be used to limit records entries on related tables Can also set Cascade Update and Delete Properties

Inner Join of 3 or more table Record sets for joins with a many-many relationship

(∞-1- ∞) will result in invalid record sets


Order Detail ID

Product ID

Date Sold Quantity

1 31 4/30/97 222 40 4/30/97 553 44 4/30/97 184 40 4/30/97 20

Product NameCategory

IDSupplier

IDProduct

IDUnits In Stock

Unit Price

Granola Gems CA 2 2 10 0.37Dingers, Cupcake BA 2 14 10 0.65Cakelets, Vanilla BA 1 15 5 0.73Cookie, Chocolate BA 1 22 12 0.60Cider mix, dry BE 11 31 34 0.12Root beer BE 10 40 21 0.31Mango Refresher BE 10 44 48 0.95Cranberry Combo BE 10 45 48 1.34

Products:

Suppliers:

Now consider the snacks database again. What type of relationships are there? Is Referential data Integrity violated for any relationship?

Orders:

Supplier ID SupplierName1 Elegance Bakery2 Overholts Baking3 Larsen Nuts9 JuJu Bee Candies10 Everest Beverages


Create a list of ProductID’s and SupplierName for all BA productsCreate a list of ProductID’s and SupplierName for all BA products

SuppliersSupplierIDSupplierName

ProductsCategoryIDProductNameUnitsinstockSupplierIDProductID

FIELD ProductID SupplierName CategoryTABLE Products Suppliers ProductsTOTALSORTSHOWCRITERIA "BA"OROR


When we join 2 tables a “master list” is createdWhen we join 2 tables a “master list” is created

These are the 1st 10 elements of the master list.The total number of elements of this list will be 8*5 or 40.

Only the records with matching supplier ids will be included when an inner join is executed.


ID

Products.Supplier

IDProduct

IDUnits In Stock Unit Price

Suppliers.SupplierID SupplierName

Granola Gems CA 2 2 10 0.37 1 Elegance Bakery

Granola Gems CA 2 2 10 0.37 2 Overholts Baking

Granola Gems CA 2 2 10 0.37 3 Larsen Nuts

Granola Gems CA 2 2 10 0.37 9 JuJu Bee Candies

Granola Gems CA 2 2 10 0.37 10Everest Beverages

Dingers, Cupcake BA 2 14 10 0.65 1 Elegance Bakery

Dingers, Cupcake BA 2 14 10 0.65 2 Overholts Baking

Dingers, Cupcake BA 2 14 10 0.65 3 Larsen Nuts

Dingers, Cupcake BA 2 14 10 0.65 9 JuJu Bee Candies

Dingers, Cupcake BA 2 14 10 0.65 10Everest Beverages


There are 7 elements created on the master list with matching foreign keys. Since supplierid 3 has no products on our product list, it does not appear anywhere on this “joined” list.

Here is the resulting record set from an Inner Join on Supplierid

Here is the resulting record set from an Inner Join on Supplierid


ID

Products.Supplier

IDProduct

IDUnits In Stock

Unit Price


Cakelets, Vanilla BA 1 15 5 0.73 1 Elegance Bakery

Cookie, Chocolate BA 1 22 12 0.60 1 Elegance Bakery



Root beer BE 10 40 21 0.31 10 Everest Beverages

Mango Refresher BE 10 44 48 0.95 10 Everest Beverages

Cranberry Combo BE 10 45 48 1.34 10 Everest Beverages


From the joined record set – Access then selects only those records that meet the specified criterion. The resulting dynaset is:

Product Name Category ID

Products.Supplier

IDProduct

IDUnits In Stock Unit Price


Cakelets, Vanilla BA 1 15 5 0.73 1 Elegance Bakery

Cookie, Chocolate BA 1 22 12 0.60 1 Elegance Bakery



Root beer BE 10 40 21 0.31 10 Everest Beverages

Mango Refresher BE 10 44 48 0.95 10 Everest Beverages

Cranberry Combo BE 10 45 48 1.34 10 Everest Beverages

Product ID SupplierName

15 Elegance Bakery

22 Elegance Bakery

14 Overholts Baking

From the resulting record set – only

those with a category of BA are

selected


FIELD SupplierName UnitsInStockTABLE Suppliers ProductsTOTAL Group by SumSORTSHOWCRITERIAOR

Write a query to summarize by supplier name the number of units in stock of that supplier’s products. Write a query to summarize by supplier name the number of units in stock of that supplier’s products.



Does the foreign key, SupplierID, need to be on the QBE grid?


The resulting dynaset:

Why isn’t Larsen’s Nuts listed with 0 UnitsInStock?

SupplierName SumOfUnitsInStock

Elegance Bakery 17

Everest Beverages 117

Overholts Baking 20

Write a query to summarize by supplier name the number of units in stock of that supplier’s products. Write a query to summarize by supplier name the number of units in stock of that supplier’s products.


For each order, list the product name, supplier name and quantity ordered For each order, list the product name, supplier name and quantity ordered

FIELD ProductName SupplierName QuantityTABLE Products Suppliers OrdersTOTALSORTSHOWCRITERIAOROR



OrdersOrderdetailidProductIdDate SoldQuantity

Does this set of joins give us a valid record set?


Product Name SupplierName Quantity

Root beer Everest Beverages 55

Mango Refresher Everest Beverages 18

Granola Gems Overholts Baking 20

Products:

Order Detail ID

Product ID Date Sold Quantity

1 31 4/30/97 222 40 4/30/97 553 44 4/30/97 184 2 4/30/97 20


IDSupplier

IDProduct

IDUnits In Stock

Unit Price

Granola Gems CA 2 2 10 0.37Dingers, Cupcake BA 2 14 10 0.65Cakelets, Vanilla BA 1 15 5 0.73Cookie, Chocolate BA 1 22 12 0.60Cider mix, dry BE 11 31 34 0.12Root beer BE 10 40 21 0.31Mango Refresher BE 10 44 48 0.95Cranberry Combo BE 10 45 48 1.34

Suppliers: Orders:

Supplier ID SupplierName1 Elegance Bakery2 Overholts Baking3 Larsen Nuts9 JuJu Bee Candies10 Everest Beverages

How does the violation of Referential Data Integrity affect the resulting dynaset?

Query result:

Documents

CS&E 1111 AcInnerJoins Inner Joins Objectives: Creating Queries with data from Multiple Tables Joining two tables using an Inner Join Referential Data