Normalization Summary

Size: px

Start display at page:

Download "Normalization Summary"

Winfred Todd
8 years ago
Views:

Normalization Summary A User View Creating the Unnormalized Table The figure above is a report (a user view) that might be produced by a database system for which the table represented by the report

1 Normalization Summary A User View Creating the Unnormalized Table The figure above is a report (a user view) that might be produced by a database system for which the table represented by the report needs to be normalized. The database designer begins by listing the variable fields that appear on the report in table form. Once the field list is determined, select a primary key. The primary field is the field (or concatenation of two or more fields) that uniquely identifies each record. The Unnormalized Table PurchaseOrder (the Extension field is removed since it is a calculated field) PurchaseOrder (PONumber, PODate, VendorNumber, VendorName, Address, City, State, ZipCode,

Once the field list is determined, select a primary key. The primary field is the field (or concatenation of two or more fields) that uniquely identifies each record.

2 Converting from Unnormalized to 1NF An unnormalized table has records in which several of the fields may have multiple values (see previous page). The important step in converting to 1NF (1 st normal form) is to identify and subsequently remove these repeating groups. Repeating Groups The figure below shows the table in 1NF (1 st normal form) in which records that had repeating groups now are separated into multiple records. A modified primary key for this modified table is created by joining fields ( PONumber and ProductNumber ) to create a concatenated key. The table name also may have to be updated (in this case from PurchaseOrder to Payables ) to reflect the new nature of the individual records. Important: In 1NF there always still will be just one table 1NF (First Normal Form) Payables (PONumber, PODate, VendorNumber, VendorName, Address, City, State, ZipCode,

Repeating Groups The figure below shows the table in 1NF (1 st normal form) in which records that had repeating groups now are separated into multiple records.

3 Converting from 1NF to 2NF To convert to 2NF (2 nd normal form) it is necessary to identify the determinants. Determinants are a listing of every possible combination of elements (fields) that make up the primary key in 1NF as in the example below. PONumber ProductNumber PONumber, ProductNumber Determinants After listing the determinants, identify the functional dependencies. Each of the non-key fields (the remaining fields that are not the determinants) rely on one of the determinants to determine their value as in the example below. Functional dependencies PONumber PODate, VendorNumber, VendorName, Address, City, State, ZipCode, Subtotal, Tax, Shipping, Discount, POTotal ProductNumber Product PONumber, ProductNumber UnitPrice, Quantity For the new 2NF (2 nd normal form) tables, the determinants are the primary keys. 2NF (Second Normal Form) Subtotal, Tax, Shipping, Discount,

PONumber ProductNumber PONumber, ProductNumber Determinants After listing the determinants, identify the functional dependencies.

4 Converting from 2NF to 3NF Within the existing 2NF tables, identify the non-key determinants. Non-key determinants are any nonkey fields that could be a primary key for other fields in one of the 2NF tables as in the example below. Non-key Determinants Subtotal, Tax, Shipping, Discount, VendorNumber After listing the non-key determinants, identify the functional dependencies. Functional dependencies are each of the remaining non-key fields that rely on the determinant(s) to determine their value as in the example below. Functional Dependencies VendorNumber VendorName, Address, City, State, ZipCode Create the new 3NF (3 rd normal form) table(s) from the determinant(s) and functional dependency(cies). Do not remove the non-key determinant(s) from their original table(s) 3NF (Third Normal Form) Vendor (VendorNumber, VendorName, Address, City, State, ZipCode) Purchase Order (PONumber, VendorNumber, Subtotal, Tax, Shipping, POTotal, PODate)

Non-key Determinants Subtotal, Tax, Shipping, Discount, VendorNumber After listing the non-key determinants, identify the functional dependencies.

5 Review The Seven Parts of a Normalization Assignment Given an assignment which requires normalization of a table, you must present the following seven required steps: 1. Show the unnormalized table: ZipCode, ProductNumber, Product, UnitPrice, Quantity, Subtotal, Tax, Shipping, Discount, 2. Identify and list the repeating groups: ZipCode, ProductNumber, Product, UnitPrice, Quantity, Subtotal, Tax, Shipping, Discount, 3. Show the table in 1NF (1 st normal form): Payables (PONumber, PODate, VendorNumber, VendorName, Address, City, State, ZipCode, 4. Identify and list the determinants and functional dependencies: PONumber PODate, VendorNumber, VendorName, Address, City, State, ZipCode, Subtotal, Tax, Shipping, Discount, POTotal ProductNumber Product PONumber, ProductNumber UnitPrice, Quantity 5. Show the table in 2NF (2 nd normal form): ZipCode, Subtotal, Tax, Shipping, Discount, 6. Identify and list the non-key determinants and functional dependencies: VendorNumber VendorName, Address, City, State, ZipCode 7. Show the table in 3NF (3 rd normal form): Vendor (VendorNumber, VendorName, Address, City, State, ZipCode) Purchase Order (PONumber, VendorNumber, Subtotal, Tax, Shipping, POTotal, PODate)

Identify and list the repeating groups: ZipCode, ProductNumber, Product, UnitPrice, Quantity, Subtotal, Tax, Shipping, Discount, 3.

South East of Process Main Building / 1F. North East of Process Main Building / 1F. At 14:05 April 16, 2011. Sample not collected

South East of Process Main Building / 1F. North East of Process Main Building / 1F. At 14:05 April 16, 2011. Sample not collected At 14:05 April 16, 2011 At 13:55 April 16, 2011 At 14:20 April 16, 2011 ND ND 3.6E-01 ND ND 3.6E-01 1.3E-01 9.1E-02 5.0E-01 ND 3.7E-02 4.5E-01 ND ND 2.2E-02 ND 3.3E-02 4.5E-01 At 11:37 April 17, 2011 At