A foundational reading that defines what keys are in relational databases, explains why they are essential for identifying and relating data, and serves as a conceptual starting point for learners before they study specific key types.
Topics
This module covers 7 topics. Open a topic to see its subtopics.
Module Content
15 items.
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A reading that explains what primary keys are, their uniqueness and non-null requirements, how to define them in SQL, and how learners and instructors can use the concept as the basis for understanding row identification in table design.
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A reading that covers how foreign keys link tables in a relational database, what referential integrity means, how foreign key constraints are declared in SQL, and how learners use this knowledge to design and maintain consistent multi-table databases.
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A reading that defines candidate keys as any minimal column or column combination capable of uniquely identifying rows, explains the relationship between candidate keys and the chosen primary key, and helps learners understand the selection process in database design.
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A reading that explains composite keys as primary keys made up of two or more columns, describes the real-world scenarios where they are necessary, and guides learners through how to define and use them in SQL table definitions.
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A reading that defines surrogate keys as system-generated identifiers added when natural data provides no practical unique identifier, compares them to natural keys, and helps learners understand when and how to apply them in database design.
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A reading that explains how SQL key constraints such as PRIMARY KEY, FOREIGN KEY, and UNIQUE are used to automatically enforce data integrity at the database level, intended to help learners understand constraint syntax and the errors that arise when constraints are violated.
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A reading that explains how SQL key constraints such as PRIMARY KEY, FOREIGN KEY, and UNIQUE are used to automatically enforce data integrity at the database level, intended to help learners understand constraint syntax and the errors that arise when constraints are violated.
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An introductory reading that defines what a key is in a relational database and explains why keys are essential for identifying rows, preventing duplicates, and linking tables, giving learners the conceptual foundation for the rest of the module.
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A lesson page on primary keys covering uniqueness and NOT NULL requirements and how to declare PRIMARY KEY constraints at the column or table level in SQL, used by learners to practice choosing and defining a table's primary identifier.
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A reading on foreign keys and referential integrity that shows how FOREIGN KEY columns reference primary or unique keys in parent tables to connect data, helping learners model relationships such as orders-to-customers and enrollments-to-students.
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A topic page defining candidate keys through the properties of uniqueness and irreducibility (minimality), guiding learners to identify all possible keys in a table and select one as the primary key.
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A lesson on composite keys made of two or more columns that are unique only in combination, with examples from junction tables and order line items so learners can recognize and declare multi-column keys.
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A practical reading on declaring PRIMARY KEY, FOREIGN KEY, and UNIQUE constraints so the DBMS enforces key rules on every insert, update, and delete, moving learners from conceptual key design to enforced data integrity.
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A consolidated module page that compiles all topics on keys — introduction, primary, foreign, candidate, and composite keys, plus constraint enforcement — for use as a single continuous reading or review reference.