Tricky~20min

The Meter Reading That Went Backwards

6 meters logged a reading lower than their previous one with no replacement on file — usage can't go backward under normal billing, which points to tampering or a bad read. 10 other meters also show a lower reading, but those had a legitimate meter swap recorded on that same row.

Tables you'll query

metersmeter_readings

What you'll learn

JOINs
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