Module 4 · Dates, windows and time Lesson 10 of 15
Dates and time in SQL
Dates are the most common filter in analytics and the one most often broken. Store them as real date columns, filter with ranges, and never compare a date to a string that only looks like one.
Worked example
WHERE created_at >= '2026-01-01' AND created_at < '2026-02-01' covers a whole month and still lets the database use an index on the column.
Your practice task
Count postings per month for the last six months, then count only the last seven days, and compare the two queries.
Do this before moving on. Reading a solution teaches the shape of it; typing it teaches you.
Key takeaway
Dates are the most common filter in analytics and the one most often broken. Store them as real date columns, filter with ranges, and never compare a date to a string that only looks like one.
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