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Lecture Comments (1)

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Post by Carl Scaglione on September 22, 2017

At he 8 minute mark of this lecture, the person to whom you refer was E. F. Codd (1923-2003).  He was seminal in developing the database normalization forms; there three basic forms with others for greater rigor in database design. There are the 12 rules for database design.  And finally, there the famous mnemonic to remember the crux of these rules:  The key, the whole key, and nothing but the key, so help me Codd.

Introduction to Databases

  • An entity is the smallest unit of information in a database
  • A Table is used to hold one type of data and can be related to other tables
  • A column in a table holds one piece of data type shared by all records, also called an “attribute”
  • A row holds all data related to one entity, also called a “record”
  • A relational database defines how data relate to each other
  • A domain constrains a column to a specific data type, i.e. int or string
  • A primary key is unique within a table and uniquely identifies a record
  • A foreign key is a primary key from another table
  • Stored Procedures are methods stored directly in the database that work on data in the database
    • They allow you to enforce business rules within your database
  • Cardinality defines the type of relationship between a table and a foreign key: One-to-One, One-to-Many or Many-to-Many
  • Optionality tells whether the relationship is mandatory or optional
  • Referential Integrity makes sure changes in one table don’t negatively affect another table
  • Database normalization allow you to optimize your database by minimizing redundancy and dependency
  • Structured Query Language (SQL) is a special-purpose programming language designed for querying and manipulating databases
  • The Microsoft version is called T-SQL
  • There are two types of queries you can make:
    • Data Definition Language (DDL) which defines and updates the structure of the data
    • Data Manipulation Language (DML) which allows you to create, modify or delete data using four keywords:
      • CREATE e.g. CREATE TABLE Employee
      • SELECT e.g. SELECT * FROM Customers
      • SET e.g. SET ZipCode = “00000” WHERE…
      • DELETE e.g. DELETE * FROM Customers WHERE…
  • The ACID test defines a valid database transaction
    • Atomicity - Each transaction is “all or nothing”
    • Consistency – Any transaction should bring the database from one valid state to another
    • Isolation – Concurrent transactions are the same as serial transactions
    • Durability – Once a transaction is committed, it stays committed
  • Standard database design follows the following steps:
    • Determine entities involved and create a table for each type
    • Determine Primary Key for each table
    • Determine non-key attributes
    • Determine relationships between tables