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For more information, please see full course syllabus of Visual Basic
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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