Exercises
1. Write a SELECT statement that returns one row for each vendor in the Invoices table that contains these columns : The vendor_id column from the Vendors table The sum of the invoice_total columns in the Invoices table for that vendor
This should return 34 rows.

2. Write a SELECT statement that returns one row for each vendor that contains these columns: The vendor_name column from the Vendors table The sum of the payment_total columns in the Invoices table for that vendor
Sort the result set in descending sequence by the payment total sum for each vendor.
3. Write a SELECT statement that returns one row for each vendor that contains three columns: The vendor_name column from the Vendors table The count of the invoices in the Invoices table for each vendor The sum of the invoice_total columns in the Invoices table for each vendor
4. Write a SELECT statement that returns one row for each general ledger account number that contains three columns: The account_description column from the General_Ledger_Accounts table The count of the items in the Invoice_Line_Items table that have the same account_number The sum of the line_item_amount columns in the Invoice_Line_Items table that have the same account_number
Return only those rows where the count of line items is greater than 1. This should return 10 rows.
Group the result set by account description. Sort the result set in descending sequence by the sum of the line item amounts.
5. Modify the solution to exercise 4 so it returns only invoices dated in the second quarter of 2014 (April 1, 2014 to June 30, 2014). This should still return 10 rows but with some different line item counts for each vendor. Hint: Join to the Invoices table to code a search condition based on invoice_date.
6. Write a SELECT statement that answers this question: What is the total amount invoiced for each general ledger account number? Return these columns: The account number from the Invoice_Line_Items table The sum of the line item amounts from the Invoice_Line_Items table
Use the WITH ROLLUP operator to include a row that gives the grand total. This should return 22 rows.
Note: Once you add the WITH ROLLUP operator, you may need to use MySQL Workbench’s Execute SQL Script button instead of its Execute Current Statement button to execute this statement.
7. Write a SELECT statement that answers this question: Which vendors are being paid from more than one account? Return these columns: The vendor name from the Vendors table The count of distinct general ledger accounts that apply to that vendor’s invoices
This should return 2 rows.