Lesson 05: Basic SQL (in MySQL)

Notes/errata/updates for Chapter 5:
See the official book errata at http://tahaghoghi.com/LearningMySQL/errata.php – Chapter 5 is pages 135-177.

If you did not load the sample databases in Chapter 3 as per page 102, you can download the file to import from http://tahaghoghi.com/LearningMySQL/Downloads/Files/Data/SQL_files_with_foreign_key_references/music.sql

On page 162, it says “In Chapter 6, we’ll discuss how to load data from existing tables or from external data sources.” but this content is in Chapter 8.

On page 169, it has an example of “DELETE FROM played;” which deletes all the rows of a table. This will not work if safe_updates are enabled. I always advise that if you truly want to do that, ALWAYS use a WHERE clause, for example: DELETE FROM played WHERE 1=1;. In this way, your query is self-documenting – it tells the reader that you intended to delete all rows. If you just have “DELETE FROM played” it is possible you meant to put a WHERE clause in but forgot.

Similarly, on page 171, it shows an example where an UPDATE with no WHERE clause is used to update all rows. I prefer the syntax UPDATE tbl SET column=value WHERE 1=1 – this broadcasts your intent.

Topics covered:
How to get table metadata with SHOW
Basic SELECT statements
– Choosing columns
– Filtering with WHERE clauses
Joining tables with INNER JOIN

Reference/Quick Links for MySQL Marinate

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