INSS 6511 Chapter 5 Normalization An Normalization example

INSS 6512 Learning Objectives What normalization is and what role it plays in the database design process About the normal forms 1NF, 2NF, 3NF, BCNF, and 4NF How normal forms can be transformed from lower normal forms to higher normal forms That normalization and ER modeling are used concurrently to produce a good database design That some situations require denormalization to generate information efficiently

INSS 6513 Normalization A process for evaluating and correcting table structure Minimize data redundancy Eliminate Anomalies

INSS 6514 Is Normalization Necessary? NO But it is helpful to maintain data integrity and consistency

INSS 6515 Anomalies (look at table 5.1) Update—requires update in multiple locations Deletion—A deletion may lose important information Insertion—Requires complete definitions, ie does see page 187 (an employee can not be entered unless he is assigned a project

INSS 6516 Normalization Process 1 st NF 2 nd NF 3 rd NF Almost for 90-98% application 3 rd NF is sufficient

INSS 6517 Dependency When an attribute value depends on attribute B then B is dependent on A A---  B or values of B can be determined by value of A, reverse may or may not be true Ex: ssn--  Name SSN, CID--  Grade

INSS 6518 Un-normalized relation Remove REPEATING groups 1st NF Remove PARTIAL dependency 2nd NF Remove TRANSIENT dependency 3rd NF Every determinant is a candidate key Boyce-CODD NF If we can convert a relation into 3NF almost 90-98% of anomalies are removed

INSS 6519 The Need for Normalization ( continued ) Structure of data set in Figure 5.1 does not handle data very well The table structure appears to work; report is generated with ease Unfortunately, the report may yield different results, depending on what data anomaly has occurred

INSS st NF Remove repeating groups ASSIGNMENT (Proj_num, proj_name(Emp_num,E_name,job_class,c hg_hours,Hour))

INSS A Dependency Diagram: First Normal Form (1NF)

INSS Second Normal Form (2NF) Conversion Results

INSS Third Normal Form (3NF) Conversion Results

INSS Un-normalized form A relation is in un-normalized form, if it contains repeating group Typically shown in parentheses Ex: PART NO DESC. VENDOR-NAME ADDRESS UNIT-COST 1234 LOGIC INTEL SAN JOSE chip LSI LOGIC SAN JOSE MEMORY INTEL SAN JOSE chip SUPPLIER (Part_no, Part_DESC, (Vendor_name, Vendor_address, Unit_cost))

INSS st NF A relation is in 1 st NF if it does NOT contain any repeating groups (Part_no, Part_DESC, (Vendor_name, Vendor_address, Unit_cost)) 1 st NF..remove repeating groups Break it into TWO relations One without repeating group and ONE with repeating group AND PK of other relation S1 (Part_no, Part_DESC) S2 (Vendor_name, Part_no, Vendor_address, Unit_cost

INSS nd NF A relation is in 2nf NF if it is in 1stNF and it does not contain any partial dependency Partial dependency: A partial dependency exists if an attribute is dependent ONLY on PART of the PK and the WHOLE PK We must examine each relation for partial dependency NOTE: A partial dependency can only exist if there are more than ONE attribute as PK

INSS S1 (Part_no, Part_DESC) S2 (Vendor_name, Part_no, Vendor_address, Unit_cost Note S1 is already in 2 nd NF since there is only attribute as PK In S2: Question is Vendor_address dependent on BOTH vendor_name AND Part_NO? Question is Unit_price dependent on BOTH vendor_name AND Part_NO?

INSS Question is Vendor_address dependent on BOTH vendor_name AND Part_NO? Answer: NO Give me vendor_no and I can find vendor_address, we do NOT need Part_No to know vendor_address, ie Vendor_address depends ONLY Vendor_name, hence the partial dependency

INSS Question is Unit_price dependent on BOTH vendor_name AND Part_NO? YES if you examine the table, price changes with vendor and part_no, ie price depnds on both Part_no AND which vendor supplies it

INSS Remove Partial Dependency VENDOR _ADDRESS VENDOR_name UNIT_PRICE PART# Create TWO tables: One with Partial dependency and other without it S21 (Vendor_name, vendor_address) S22(Vendor_name, Part_no, Unit_price)

INSS rd NF A relation is in 3 rd NF if it is in 2 nd NF and it does not contain any transitive dependency Transitive dependency: A transitive dependency exists when some of the non- key attributes are dependent on other non- key attributes

INSS So far we have three relations that are in at least 2 nd NF S1 (Part_no, Part_DESC) S21 (Vendor_name, vendor_address) S22(Vendor_name, Part_no, Unit_price) S1, S21 & S22 are also in 3 rd NF since there is ONLY ONE non_key attribute and transitive dependency can NOT exist

INSS ERD PARTPART-SUPPLIED VENDOR

INSS Q6/p 84

INSS Q8/P187 Table P5.8 Sample ITEM Records Attribute Name Sample Value ITEM_ID ITEM_LABELHP DeskJet 895CseHP TonerDT Scanner ROOM_NUMBER BLDG_CODENTC CSF BLDG_NAMENottooclearNottoclearCanseefar BLDG_MANAGERI. B. Rightonit May B. Next

INSS ITEM_DESCRIPTION BLDG_CODE BLDG_NAME BLDG_MANAGER ITEM_ID BLDG_ROOM Problem 8 Solution

INSS ITEM_DESCRIPTION BLDG_CODE BLDG_NAME EMP_FNAME EMP_INITIAL BLDG_NAME BLDG_MANAGER BLDG_CODE EMP_CODE EMP_LNAME Problem 9 Solution: All tables in 3NF ITEM_ID BLDG_ROOM ITEM_DESCRIPTIONITEM_ID BLDG_ROOMBLDG_CODE EMP_CODE

INSS 65128

INSS Denormalization Reversing normalization i.e from 3 rd NF to 2 nd NF Or 2 nd to 1 st NF

INSS Convert into 3NF INVOICE (Inv_num, cust_num,lastname,Firstname,street,city,s tate,zip,date,(partnum, description,price,numshipped))