Identify features of relational data
Relational data refers to the type of data that can be organized into a table structure with related values connected to each other. This table structure consists of rows and columns, where each row represents a record, and each column represents a particular type of data called a file or attribute. Here are some of the key features of relational data:
- Tables: In a relational database, all data is stored in a table, which is structured in rows and columns. Each column represents a type of data (an attribute), and each row repre-sents an instance of that data (a record). For example, in a Student table, columns could
30 CHAPTER 2 Identify considerations for relational data on Azure
be StudentID, Name, and Major, while each row would represent an individual student’s data.
- Keys: Keys are a crucial feature of relational data. A primary key is a unique identifier for a row in the table. Foreign keys establish relationships between tables. For instance, a CourseID might be a foreign key in an Enrollments table, linking it to the Courses table.
- Normalization: This is the process of organizing data to minimize redundancy and avoid data anomalies, such as update errors. It involves decomposing a table into less redundant tables without losing information.
- Relationships: The relational model allows for relations among tables, typically through foreign keys. Relationships can be one-to-one, one-to-many, or many-to-many. For example, one student (in the Student table) can be enrolled in many courses (in the Courses table); this is a one-to-many relationship.
- Data integrity: Relational database enforces data integrity rules, ensuring the accuracy and consistency of data. These include entity integrity (no duplicate rows), referential integrity (consistency across relationships), and domain integrity (data types and value consistency).
- SQL: SQL is used for querying and manipulating the data stored in a relational database.
In Table 2-1, each row represents a student with a unique Student_id, their name is Student_ Name, and the ID of the course in which they’re enrolled is Course_id. The Course_id in Table 2-1 is a foreign key that connects Table 2-1 to Table 2-2.
In Table 2-2, each row represents a course with a unique Course_id and its name is Course_ Name. The Course_id in this table is the primary key.
TABLE 2-1 Student table
TABLE 2-2 Course table
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In the context of Azure, there are several services that are built on the relational model, such as Azure SQL Database and SQL Server on Azure VMs. These services allow you to work with relational data using SQL for managing and manipulating the relational data.
The relational concept is at the heart of most traditional database systems, and understand-ing it is key to becoming proficient in any database-related work, especially when working with Azure’s data services.