My multiple choice questions are for the SQL lessons.
Question 1: SQL ‘UNION’
Which of the following SQL commands is used to combine the results of to queries so that all of the output of each query is present in the final result?
LEFT INNER JOIN
LEFT OUTER JOIN
Question 2: SQL ‘UNION’
In the aggregation portion of the lesson, we saw that
avg can be used to get the mean of a set of values. What does the
avg function return when called on the values 0.0, 1.0, 2.0, 3.0, and
- An error
The first distractor (‘an error’) is meant to catch the misconception that the
avg function cannot be run on a set that includes
null values. The second distractor (1.5) could be chosen if the student thinks that
null values are ignored (i.e. (0.0+1.0+2.0+3.0)/4 = 1.5). The third distractor (2.0) might be chosen if the student thinks that both zeroes and
null values are ignored in the
avg function. The second answer (1.2) is correct.