Database guides

The ideas behind the lab, explained with diagrams and real query results. Read a guide, then practise it straight away.

• 6 min readCrow's Foot notation explainedLearn the four Crow's Foot symbols, how to read a relationship in both directions, how to resolve many-to-many relationships and where foreign keys go, with diagrams.
• 7 min readDatabase normalization: 1NF, 2NF and 3NFA worked example of normalizing a library loans sheet from unnormalized form to Third Normal Form, explaining repeating groups, partial dependencies and transitive dependencies.
• 6 min readSQL joins explained with examplesHow INNER JOIN and LEFT JOIN work, how to find rows with no match, and how to join several tables, with runnable examples and their results on a sample store database.
• 5 min readGROUP BY and HAVING explainedHow GROUP BY turns rows into groups, how aggregate functions like COUNT and SUM work, and the difference between WHERE and HAVING, with runnable examples.