Chapter 5 Exercise 37

37. For the month of March, list the percentage of visits covered by each type of insurance company.

SELECT Visit.InsuranceCompany, Count(Visit.VisitID) AS CountOfVisitID,
Count(Visit.VisitID)/
(
SELECT Count(VisitID)
FROM Visit
WHERE Visit.VisitDate BETWEEN #3/1/2013# And #12/31/2013#
) AS PCT
FROM Visit
WHERE (((Visit.VisitDate) Between #3/1/2013# And #12/31/2013#))
GROUP BY Visit.InsuranceCompany;