10_ER_Model - CSI 1306 F Computing Concepts for Business...

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Unformatted text preview: CSI 1306 F Computing Concepts for Business LECTURE 10: THE RELATIONAL DATA MODEL Data Organizations and individuals generate data describing their assets and activities This data is used in The conduct of day-to-day operations Planning Decision making To be accessible, the data must be stored in an organized manner Data Examples of organized manual storage A telephone book : stores names, addresses and phone numbers for individuals and organizations in name sequence so that any telephone number for an individual or organization can be quickly accessed by name Employee cards : each card stores information about one employee; the cards are filed in name sequence so they can be accessed by name Part cards : each card stores information about one part; the cards are filed in part number sequence so that the card for a specific part can be accessed by its part number Parts Data Part 5098 Qty on Hand Part 4982 Qty on Hand 49 Part 3876 Qty on Hand 256 Widget 989 Cost : $5.49 EOQ EOQ 50 Supplier : EOQ 300 100 Joes Widgets Data Files Each entry on the card is a field Each card is a record The collection of cards is a data file For computer storage and access, we could store the parts cards as a series of records in a data file Data Files Observe that each record has a field (shown in gray) whose value is unique This field is called the primary key field (PK) In our example, the primary key field is the part number field We can access information about a specific part by using its PK (part number) to find its record in the file In general, the PK of a set of data (table) is the minimal set of fields that makes each record unique . Data Files If we were to store the parts information in an Excel worksheet Each row would represent a record Each column would represent a field The part number column would contain the primary key All entries in the worksheet would represent a data file Data Files We could have A file of records for library books  With fields for book number, title & author A file of records for parts  With fields for part number, description, cost & location A file of records for customers  With fields for customer number, name & address A file of records for students  With fields for student number, name, address & phone number A file of records for courses  With fields for course code, name & hours Data Files Typically, a data file has relationships with other data files When a sales order is placed by a customer to purchase parts...
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10_ER_Model - CSI 1306 F Computing Concepts for Business...

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