Use ONE SQL statement to show the total number of actual hours for each customer. In the output, show customer id and the total number of actual hours for each customer.

Which statement is true of web-based social media? a. they allow consumers to interact with and update content. b. they cannot be updated easily, as compared to print media. c. they are expensive to produce and maintain, as compared to print and television. d. they can exist independent of the internet.

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

Where can page numbers appear? check all that apply. in the header inside tables in the footer at the bottom of columns at the top of columns