Database Design Course Materials

Database Design Design Table For Storing Data A. Database Database —⊳ Database is an organized collection of structured Data information, or data, typically stored electronically in a computer system. A database is usually controlled by a database management system (DBMS) Database Has 3 Component: 1. Entities An entity in a database is a thing, place, person or object that is independent of another 2. Row or Record A data record within a table. Each row, which represents a complete record of specific item data, holds different data within the same structure. 3. Column/Field A column is a collection of cells aligned vertically in a table. A field is an element in which one piece of information is stored, such as the received field B. Appropriate Primary Key A primary key, also called a primary keyword, is a column in a relational database table that's distinctive for each record The data type of a primary key should be a numeric, an integer or a short, fixed-width character. Uniqueness. A primary key must have a unique value, which implies that no other row in the table has the same value in the column. C. Appropriate Composite Key A composite key is a candidate key that consists of two or more attributes (table columns) that together uniquely identify an entity occurrence (table row) We can user composite key which from a combination of two or more columns in a table that can be used to uniquely identify each row in the table D. The Important of Data Types A data type is an attribute associated with a piece of data that tells a computer system how to interpret its value. Understanding data types ensures that data collected in the preferred format and the value of each property is as expected. 1. Data Representation Data types define how various types of data are stored in memory and how they are interpreted by the computer. Different data types allow the computer to understand and process data appropriately. For example, integers, floating-point numbers, characters, and strings are all represented differently in memory. 2. Memory Allocation Data types determine the amount of memory allocated for each variable or data element. Using appropriate data types ensures efficient memory usage, as allocating too much memory can waste resources, while allocating too little can lead to data truncation or loss. 3. Data Validation and Integrity Data types help in enforcing rules for the acceptable values that a variable can hold. For example, if a variable is declared as an integer, the programming language will prevent storing non-integer values into that variable, ensuring data integrity and reducing the risk of bugs and errors. E. Entity Relationship Diagram Entity Relationship Diagram, also known as ERD, ER Tables Diagram or ER model, is a type of structural diagram for use in database design. An ERD contains different symbols and connectors that visualize two important information: The major entities within the system scope, and the inter-relationships among these entities. How to create ERD: 1) Determine the Entities in Your ERD. 2) Add Attributes to Each Entity. 3) Define the Relationships Between Entities. 4) Add Cardinality to Every Relationship in your ER Diagram. 5) Finish and Save Your ERD