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i have now studied more than 20 mysql and sql books and find this to be excellent and one of the three most useful because it explains and supplies working code that you can experiment with and write variations on for your purposes.
Not a first book on SQL (obvious from the title), but GREAT as a second one, with plenty of practical advice for designing a database and for writing efficient SQL code. I most enjoyed chapters 5 (Aggregation) and 6 (Subqueries), with a special mention for moving aggregates (Item 39). One notable omission is the absence of coverage of assertions, which are not even mentioned. As a plus, it's one of the very few books that makes a clear distinction between Standard (ANSI/ISO) SQL and various dialects (SQL Queries for Mere Mortals also does this, to a lesser extent).