SQL pattern

NULL & Unknown

4 problemsin this pattern, climbing easy → medium → hard. Pick wherever you're calibrated. Read the P02 tutorial →

Easy

0 / 2 solved

Medium

0 / 1 solved

Open orders (including NULL status)
SQL · ~7 min
NEW

Hard

0 / 1 solved

Customers with any order that isn't paid
SQL · ~8 min
NEW