Questions

1. What is a CTE?
2. Can one CTE use other CTEs?
3. Can a CTE reference itself?
4. How do we insert rows into several tables at once?
5. Is there a way to specify the order of execution of CTEs?
6. What is the difference between grouping and aggregation, and using window functions?
7. How do we calculate a moving average of a field for each row, taking three rows before and three rows after?
8. How do we calculate the difference between the value of a field in the current row and the average of the previous and the next rows for each row?
9. Can window functions be combined with aggregating functions?
10. What is the purpose of the DISTINCT ON clause?
11. How do we get a sample of data from a database table?
12. How do we get a sequence of numbers using a SELECT query?
13. Can a subquery (not a CTE) refer to another subquery?
14. How do we use several sets of expressions in a single GROUP BY clause?

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