The Relational Model & SQL

Tables, keys, joins & declarative queries

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How the relational model organizes data into tables linked by keys, and how SQL lets you query, join, and normalize that data declaratively.

By the end, you can

Explain why a database is preferred over a flat file for concurrent, integrity-critical, queryable, large-scale data.
Define relation, tuple, and attribute using Codd's terminology.
Distinguish a primary key from a foreign key and describe what each enforces.
Describe what a JOIN does and how inner join differs from left join.
Map the relational algebra operators σ, π, and ⋈ to their SQL clause equivalents.
Write a multi-clause SQL query using SELECT, FROM, JOIN, WHERE, GROUP BY, HAVING, and ORDER BY.
State the logical execution order the query engine uses and explain why HAVING differs from WHERE.
Identify whether a statement is DDL or DML, and name the three DML operations.
Recognize the three anomalies caused by redundancy and explain how normalization eliminates them.
State the rule each normal form (1NF, 2NF, 3NF) enforces.

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