SMG IS 223 Lecture Notes - Lecture 14: Unique Key, Foreign Key, Data Redundancy

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24 May 2018

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o Fields from one table are present in other tables to form relationships

o Fields can be designated types (integer, date, varchar)

• Primary Key

• Column (s) in each table/file used to uniquely identify each record

o Many tables will utilize multiple columns (fields) to accomplish this level of

uniqueness

• Every table must have a primary key

• Foreign Key

• Column (s) in one table that is the primary key of another table

• Although the foreign key is defined in the “child” table, it refers to the primary key in the

“parent” table

• ERD is the blueprint/logical model

• Conversions of ERDs with Access

• Entities become tables

• Attributes become table columns

• Add foreign keys (create table columns for foreign keys)

• Create intermediary tables for many-to-many relationships

• Tables need to be singular, not plural

• Data Normalization

• Designing how data is stored to reduce data integrity problems

• Limiting data redundancy

• CREATING INTERMEDIARY TABLE

•

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