Fellow student response! The context for Worksheet 2 was the same as Lab 2 so I used the data provided for that lab on the Jinhong server to test the queries you proposed and this is what I found:

1. Not sure why this is. All I can say for sure is that for the data provided in Lab 2, both the 'AND' statement in the solution and 'OR' statement you have provided will give the same result. I tried some other updates and inserts to see if the results would change but I just ended up confusing myself more so I won't put them here. Hopefully someone else can provide some further clarification?

2. This alternative query will not give the same result as the solution because the 'WHERE' clause is executed before the 'HAVING' clause. This means the alternative query knocks out any tuples that have null city/phone fields and then checks that count(cust_id)>2, rather than the solution which checks for one or the other on the same line. Hope that helps :>