Know Your Data
The importance of understanding the data model that you are working in cannot be overstated
Real-world databases are messy; most database systems remain in service in an organization for decades
Know the Problem
Understand the question you are attempting to answer
Information reporting requests will come from a range of sources; may be one-time events or ongoing operations within an application
Build clauses in the following order:
FROM
WHERE
GROUP BY
HAVING
SELECT
ORDER BY