Function COUNT
Function AVG
Functions SUM, MAX, MIN
Instruction
Fine. Again, if we don't like to get NULL as a result, we can use COALESCE to replace it with any value of our choice:
SELECT COALESCE(SUM(price), 0) FROM project;
If all prices happen to be NULLs, the above query will return 0 and not a NULL. Note that this time you can also write:
SELECT SUM(COALESCE(price, 0)) FROM project;
and the result will stay the same.
Exercise
Show translator ids with the sum of the prices of all the projects they have completed (as sum). Exclude project_id = 13 so that one of the translators has NULL prices only. Instead of that NULL sum, show 0.
Stuck? Here's a hint!
Group the rows by the translator id and use COALESCE.
