JustLee DataBase Referential Integrity

Dr. Chen, Business Database Systems

JustLee DataBaseReferential Integrity

Jason C. H. Chen, Ph.D.Professor of MIS

School of Business AdministrationGonzaga UniversitySpokane, WA 99258

[email protected]


Customer# LastName FirstName Address City State Zip Referred Region Email

NUMBER(4) VARCHAR2(10) VARCHAR2(10) VARCHAR2(20) VARCHAR2(12) VARCHAR2(2) VARCHAR2(5) NUMBER(4) CHAR(2) VARCHAR2(30)

Order# Customer# OrderDate ShipDate ShipStreet ShipCity ShipState ShipZip ShipCost

NUMBER(4) NUMBER(4) DATE DATE VARCHAR2(18) VARCHAR2(15) VARCHAR2(2) VARCHAR2(5) NUMBER(4,2)

CUSTOMERS

ORDERS

Q1: Identify pk and fk

Q2: Identify the relationship (“cardinality”) between “CUSTOMERS” and “ORDERS”


Customers and Orders Entities with Referential Integrity


Customer# LastName FirstName Address City State Zip Referred Region Email

NUMBER(4) VARCHAR2(10) VARCHAR2(10) VARCHAR2(20) VARCHAR2(12) VARCHAR2(2) VARCHAR2(5) NUMBER(4) CHAR(2) VARCHAR2(30)

Order# Customer# OrderDate ShipDate ShipStreet ShipCity ShipState ShipZip ShipCost

NUMBER(4) NUMBER(4) DATE DATE VARCHAR2(18) VARCHAR2(15) VARCHAR2(2) VARCHAR2(5) NUMBER(4,2)

CUSTOMERS

ORDERS

pk

pk fk

Q2: Identify the relationship (“cardinality”) between “CUSTOMERS” and “ORDERS”

Q1: Identify pk and fk


ORDERS

pk

fkpk

Q1: Can we “create” ORDERS#1 (100) if CUSTOMERS#5 (1005) is not created? ? Why?


ORDERSfk

pk

pk

Q2: Can we “delete” CUSTOMERS#5 (1005) if ORDERS#1 (100) is still in the database? Why?


ORDERSfk

pk

pk

Order of Entering Data: CUSTOMERS ORDERSThe table with pk (e.g., customers) should be created first before the table with fk (orders)

Order of Deleting Data: ORDERS CUSTOMERSThe table with fk (orders) should be deleted first before the table with pk (customers)

Referential Integrity

Do we have (or even want) to manually enforce the data (referential) integrity?Yes/No. Why? How?


pk

pk fk

Customers#5

orders#1

Can we “create” orders#1 if customers#5 is not created? Why?

Can we “delete” customers#5 if orders#1 is still in the database? Why?


Assignment on JLDB for Referential Integrity

• 1) Identify pk, fk etc.• 2) Identify “Order of Entering Data”• 3) Identify “Order of Deleting Data”


JustLee DDL (Original one) See “Partial Solution” on the next slide


Partial Solution


JustLee DDL (Original one)


Customer# LastName FirstName Address City State Zip Referred Region EmailNUMBER(4)

VARCHAR2(10) VARCHAR2(10)

VARCHAR2(20)


VARCHAR2(5)

NUMBER(4)

CHAR(2) VARCHAR2(30)

Order# Customer# OrderDate ShipDate ShipStreet ShipCity ShipState ShipZip ShipCostNUMBER(4) NUMBER(4) DATE DATE VARCHAR2(18) VARCHAR2(15) VARCHAR2(2) NUMBER(4) NUMBER(4,2)

CUSTOMERSpk

ORDERSfkpk

ORDERSOrder# (pk)

.

.

CUSTOMERSCustomer# (pk)

.

.

ORDERSOrder# (pk)

.,

CUSTOMERSCustomer# (pk)

.

.


Using the FOREIGN KEY ConstraintReferential Integrity

• Requires a value to exist in the referenced column of another table

• NULL values are allowed• Enforces referential integrity• Maps to the PRIMARY KEY in parent table

Customer# LastName FirstName Address … Region

Order# Customer# OrderDate … ShipZip ShipCost

customers

orders

pk

fkpk


Using the FOREIGN KEY Constraint Referential Integrity (cont.)

• You cannot delete a value in a parent table (pk) referenced by a row in a child table (fk)

Customer# LastName FirstName Address … Region

Order# Customer# OrderDate … ShipZip ShipCost

customers

orders

pk

fkpk


customers

RULES: 1. You can’t add a record to TABLE- (or the table with fk, e.g., orders)

unless there is a corresponding record in TABLE-1 (or the table with pk).

2. You can’t delete a record in TABLE-1 (or the table with pk, e.g., customers) if there is a record in TABLE- (or the table with fk).

Order of entering data into the database: customers orders Order of deleting data from the database: orders customers

orders

pk

fkpk

customer# LastName … Referred Region1001 MORALES NULL SE… …

1005 GIRARD NULL NW1020 FALAH NULL NE

Order# customer# … ShipZip ShipCost1000 1005 98114 2.00… … …

1003 1001 32328 4.001012 1007 49002 6.00

Referential Integrity


Referential Integrity• The table with pk (e.g., customers) should

be created first before the table with fk (orders)

• The table with fk (orders) should be deleted first before the table with pk (customers)

• How to maintain the “Referential Integrity” in an efficient way?

• Answer: include “constraints” in the DDL.


STUDENT pk fk

s_id s_last … s_pin f_id 100 Miller 8891 1 … …

105 Connoly 9188 3 FACULTY pk fk

f_id f_last … loc_id … f_image 1 Cox 53 cox.jpg … … … 5 Brown 57 brown.jpg

LOCATION pk

loc_id bldg_code room capacity 45 CR 101 150 … … 57 LIB 222 1

TABLE-1 TABLE- (FACULTY) (STUDENT)

RULES: 1. You can’t add a record to TABLE- (or the table with fk,

e.g., STUDENT) unless there is a corresponding record in TABLE-1 (or the table with pk).

2. You can’t delete a record in TABLE-1 (or the table with pk, e.g., FACULTY) if there is a record in TABLE- (or the table with fk).

Order of entering data into the database: LOCATION FACULTY STUDENT Order of deleting data from the database:STUDENT FACULTY LOCATION




VARCHAR2(20)


VARCHAR2(5)

NUMBER(4)



CREATE TABLE Customers(Customer# NUMBER(4),LastName VARCHAR2(10) NOT NULL,FirstName VARCHAR2(10) NOT NULL,Address VARCHAR2(20),City VARCHAR2(12),State VARCHAR2(2),Zip VARCHAR2(5),Referred NUMBER(4),Region CHAR(2),Email VARCHAR2(30), CONSTRAINT customers_customer#_pk PRIMARY KEY(customer#), CONSTRAINT customers_region_ck CHECK (region IN ('N', 'NW', 'NE', 'S', 'SE', 'SW', 'W', 'E')) );

CUSTOMERSpk

ORDERSfkpk




VARCHAR2(20)


VARCHAR2(5)

NUMBER(4)



CREATE TABLE Orders (Order# NUMBER(4), Customer# NUMBER(4), OrderDate DATE NOT NULL, ShipDate DATE, ShipStreet VARCHAR2(18), ShipCity VARCHAR2(15), ShipState VARCHAR2(2), ShipZip VARCHAR2(5),ShipCost NUMBER(4,2), CONSTRAINT orders_order#_pk PRIMARY KEY(order#), CONSTRAINT orders_customer#_fk FOREIGN KEY (customer#) REFERENCES customers(customer#));

CUSTOMERSpk

ORDERSfkpk



ORDERS

Order# Item# ISBN Quantity PaidEachNUMBER(4) NUMBER(2) VARCHAR2(10) NUMBER(3) NUMBER(5,2)

ORDERITEMS

CREATE TABLE ORDERITEMS ( Order# NUMBER(4), Item# NUMBER(2), ISBN VARCHAR2(10), Quantity NUMBER(3) NOT NULL, PaidEach NUMBER(5,2) NOT NULL, CONSTRAINT orderitems_order#_item#_pk PRIMARY KEY (order#, item#), CONSTRAINT orderitems_order#_fk FOREIGN KEY (order#) REFERENCES orders (order#) , CONSTRAINT orderitems_isbn_fk FOREIGN KEY (isbn) REFERENCES books (isbn) , CONSTRAINT oderitems_quantity_ck CHECK (quantity > 0) );

ISBN Title PubDate PubID Cost Retail Discount CategoryVARCHAR2(10) VARCHAR2(30) DATE NUMBER(2) NUMBER(5,2) NUMBER(5,2) NUMBER(4,2) VARCHAR2(12)

BOOKSpk

fkCpk, fk cpk

pk

JustLee DataBase Referential Integrity

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