Lecture_2_Relational_print.pptx - Data Management Visual...

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Data Management & Visual Analytics MSCI:6050 FALL 2019 LECTURE 2: RELATIONAL MODEL 1
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Reminder HW1 HW2 Available on ICON 2
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Review - ER diagram
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Steps of Data Modeling Conceptual Data Model o Capture the nature of relationships among data/objects o It is about understanding the business rules o A symbolic model – easy to understand by human o An important task for database designers Logical Data Model o Transform the conceptual model into a logical representation o It is about creating the database structure o Logically well-defined and can be understood by computer s o Focus of data analysts Physical Data Model o Translate the logical model into technical specifications for storing/retrieving data o It is about storing data to achieve data processing efficiency and data quality o Database users and data analysts usually do not worry about this step 4 Cust_ID Cust_Name Address 101 David Hills 102 Mary Lee CUSTOMER Index and file organization on disk
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Level 2: Relational Data Model (Logical) The way in which data is logically organized in a Relational Database Store data in two dimensional tables and connect them using “Foreign keys” Basic concepts you need to know: Relation, relational schema, text and graphical representations Primary keys, foreign keys, integrity constraints Normal Forms 5
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Overview Relational schema: a set of relational tables and keys/constraints between tables Rows, columns, primary keys, foreign keys, constraints Representations, symbols Converted from ER Model Entity types -> New relation Relationships -> Foreign keys 6
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Logical Data Model 7 Relational Data Model o Represent data in the form of relations Object-oriented Data Model o Based on object classes Multidimensional Data Model o View data in the form of cubes Document-store Data Model o Represent data in terms of key-document pairs
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Relational Data Model Historical Background o First introduced in 1970 by E. F. Codd, an IBM research fellow o Has a solid theoretical foundation (set theory) o Widespread commercial success in 1980s o By far the most commonly used in various database applications Three Components 8
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Relation Definition o A named , two-dimensional table of data o Consist of a set of named columns and unnamed rows o Each column represents an attribute or a field o Each row corresponds to a record or an instance o Contain information about one specific entity/relationship type Properties o Unique table name o Each entry/cell is atomic (or single valued ), i.e., no multivalued attributes o Each column has a unique name o Each row is unique (no duplicate rows) 9
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Multivalued Attributes 10 Remove multivalued attributes from tables
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Relational Keys (1) Primary Key (PK) o An attribute or a combination of several attributes that uniquely identifies each row o Each relation must have a primary key o May be the same as an entity’s identifier 11
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Relational Keys (2) Composite key o A primary key o
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  • Fall '19
  • Entity-relationship model, Database normalization

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