Learn Standard SQL Functions | Interactive Course | Vertabelo Academy

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13/37 COUNT DISTINCT with expression and GROUP BY

1. Introduction

2. Table translator

3. Table project

4. Count all rows

5. COUNT with column

6. COUNT(*) vs. COUNT(column) – practice

7. COUNT with expression

8. COUNT DISTINCT

9. COUNT DISTINCT with expression

10. COUNT and GROUP BY

11. COUNT and GROUP BY – additional practice

12. COUNT DISTINCT and GROUP BY

13. COUNT DISTINCT with expression and GROUP BY

14. Common mistake: COUNT(*) and LEFT JOIN

15. COUNT – additional exercise 1

16. COUNT – additional exercise 2

17. Function AVG

18. AVG and GROUP BY

19. AVG and NULLs

20. AVG and NULLs only

21. AVG with COALESCE

22. COALESCE with AVG

23. AVG and DISTINCT

24. ROUND and AVG

25. AVG – additional exercise

26. Function SUM

27. SUM with NULLs only

28. SUM and COALESCE

29. SUM and DISTINCT

30. MAX and MIN

31. SUM, MAX and MIN – exercise

37. Congratulations

As you may already suspect, COUNT(DISTINCT expression) can be also used together with GROUP BY. Try it out in the exercise below.

The rate per word is the price divided by the number of words. For every translator, show ID together with number of distinct rates per word they used in their projects. Name the second column rates_no.

To obtain the rate per word, use CAST(price AS numeric)/words.

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