<\/span><\/h3>\n\n\n\nAs mentioned previously, relational databases comprise two-dimensional tables with rows and columns. Each table represents a related data collection, with columns defining the attributes and rows representing records. For example, a “Customers” table may have columns like first name, last name, email, city, etc. Each row would be a record of an individual customer.<\/p>\n\n\n\n
Tables enable the structured organization of data and establish relationships between different entities.<\/p>\n\n\n\n
<\/span>Keys<\/span><\/h3>\n\n\n\nKeys are critical to establishing relationships between database tables:<\/p>\n\n\n\n
\n- Primary Key<\/strong>: Uniquely identifies each row in a table, such as a customer ID or order number.<\/li>\n\n\n\n
- Foreign Key<\/strong>: The linking field that connects two tables usually references the primary key of another table.<\/li>\n\n\n\n
- Composite Key<\/strong>: A primary key composed of two or more columns, used when no single column uniquely identifies a row.<\/li>\n<\/ul>\n\n\n\n
Proper use of keys eliminates duplicative data and maintains data integrity when linking tables.<\/p>\n\n\n\n
<\/span>Relationships<\/span><\/h3>\n\n\n\nTable relationships represent the association between two tables, linked by a standard key:<\/p>\n\n\n\n
\n- One-to-One<\/strong>: Each record in one table is linked to one and only one record in the other table.<\/li>\n\n\n\n
- One-to-Many<\/strong>: A record in one table can be linked to multiple records in another\u2014a most common type of relationship.<\/li>\n\n\n\n
- Many-to-Many<\/strong>: Records in both tables can be linked to multiple records in the other table. Requires a third junction table.<\/li>\n<\/ul>\n\n\n\n
Proper table relationships reduce data redundancy and improve the structure of a database.<\/p>\n\n\n\n
<\/span>Normalization<\/span><\/h3>\n\n\n\nNormalization is the process of optimizing table structures to minimize duplicative data and optimize relationships:<\/p>\n\n\n\n
\n- 1st Normal Form<\/strong>: Eliminate repeating data groups and create separate tables.<\/li>\n\n\n\n
- 2nd Normal Form<\/strong>: Create tables for subgroups with dependencies linked with foreign keys.<\/li>\n<\/ul>\n\n\n\n
Higher levels of normalization improve database flexibility and reduce anomalies but can impact performance. Tradeoffs are often made based on the application.<\/p>\n\n\n\n
<\/span>ACID Compliance<\/span><\/h3>\n\n\n\nACID compliance refers to four fundamental properties of database transactions:<\/p>\n\n\n\n
\n- Atomicity<\/strong> – Transactions are all or nothing, either completed fully or rolled back.<\/li>\n\n\n\n
- Consistency<\/strong> – Transactions must follow schema rules and maintain data integrity.<\/li>\n\n\n\n
- Isolation<\/strong> – Transactions execute independently without interference.<\/li>\n\n\n\n
- Durability<\/strong> – Completed transactions persist even in cases of system failure.<\/li>\n<\/ul>\n\n\n\n
Compliance helps ensure database transactions’ accuracy, consistency, and reliability.<\/p>\n\n\n\n
<\/span>Advanced Database Topics<\/span><\/h2>\n\n\n\n<\/span>Data Warehousing<\/span><\/h3>\n\n\n\nA data warehouse is a central repository of integrated data from multiple sources optimized for analysis and reporting. Key aspects include:<\/p>\n\n\n\n