Sams Teach Yourself SQL in 21 Days, Fourth Edition

Day 7

Quiz

1:	In the section “Nesting Subqueries,” the sample subquery returned several values: LE SHOPPE BIKE SPEC LE SHOPPE BIKE SPEC JACKS BIKE Some of these are duplicates. Why aren't these duplicates in the final result set?
A1:	The result set has no duplicates because the query that called this subquery SELECT ALL C.NAME, C.ADDRESS, C.STATE,C.ZIP FROM CUSTOMER C WHERE C.NAME IN returned only the rows where NAME was in the list examined by the statement IN. Don't confuse this simple IN with the more complex JOIN.
2:	Are the following statements true or false? The aggregate functions SUM, COUNT, MIN, MAX, and AVG all return multiple values. The maximum number of subqueries that can be nested is two. Correlated subqueries are completely self-contained. ...