-- Wrong: WHERE cannot use SUM() -- Right: SELECT customer_id, SUM(invoice_total) as total FROM invoices GROUP BY customer_id HAVING total > 500;
is not a reference encyclopedia (you don't need to memorize 100 functions). It is a toolkit . By the end of the 8+ hours, you will write queries faster, debug errors logically, and think in "sets" of data rather than rows. sql programming with mosh
: Mastering the SELECT clause, filtering with WHERE , and sorting with ORDER BY . -- Wrong: WHERE cannot use SUM() -- Right:
