These properties can lead to complications in maintaining the integrity of the database, as changes in the real world need to be reflected accurately in the database. Natural keys are derived from real-world data (like email addresses or social security numbers) and may pose challenges due to their potential to change over time and lack of inherent uniqueness. Explain why natural keys may be a bad idea. Meanwhile, the UniversityFK is a foreign key. StudentIDĮxample: In the relation above, StudentID is a primary key. This relationship enables the representation of relational data, linking records between tables and maintaining data integrity across the database. A foreign key, on the other hand, is a reference in one table to a primary key in another table. It ensures that each record can be uniquely identified. Explain what a primary key is, and how it is related to a foreign key.Ī primary key is a unique identifier for each record in a database table. For example, when a student enrolls in Texas Tech University, all students enrolled in the university will need their “Number of Students” column to be updated.Ĥ. Moreover, any data related to the University column, (ex: Number of Students) will need to be updated for every unique entity. This is problematic as this means that the University entities will take up additional space every time an entity (not only the Student entity, but other entities as well) has any sort of association with the university entity. In this case, however, it is represented twice in the University column. Simply put, Texas Tech University, an entity that’s not a student, and is a distinct entity, should not be represented twice. Let’s look at the following table, for example. In simpler terms, a distinct entity should only be represented once. By dividing a database into multiple related tables and ensuring that each table represents one concept or entity, normalization helps prevent inconsistencies and anomalies in data. Normalization, a process of organizing data in a database, aims to reduce redundancy and improve data integrity. Why does normalization help preserve data integrity? Additionally, strings can have issues with case sensitivity and whitespace differences, making them less reliable as unique identifiers. A VARCHAR(256) string would, in the worst case, take 256 times more processing power to index and compare. Strings, however, take O(n) time to evaluate, where n is the length of the string. Integers are easy to compare, often taking O(1) time to evaluate. They usually require more memory and are slower to compare and sort compared to integer keys. Strings are generally avoided as keys in databases for efficiency reasons. The uniqueness of tuples in a relation is often enforced by a key. Relations are defined by a schema, which describes the types of the attributes. Each tuple (row) in a relation represents a distinct item or entity, and each attribute (column) represents a property of that entity. It’s essentially a table in the context of relational databases. In database terminology, a relation is a set of tuples having the same attributes.
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