SQL (5)

1. DELETE

DELETE p1 FROM Person p1, Person p2
    WHERE p1.email = p2.email AND p1.id > p2.id

▲ DELETE removes the whole row(s) that fulfils the target.

2. DATEDIFF

SELECT w1.id FROM Weather w1, Weather w2
WHERE w1.temperature > w2.temperature AND DATEDIFF(DAY, w1.recordDate, w2.recordDate) = -1

▲ DATEDIFF returns the time unit (e.g. hour, day, year) difference between two dates.

DATEDIFF(DAY, w1.recordDate, w2.recordDate) = -1 means day difference between w1 date and w2 date is 1 day.

Thank you for completing this tutorial!

See you in SQL (6).

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