Question: What percentage of people named Mary who wants Receive Email promotions of AdventureWorks and selected partners are store contacts?
SQL: SELECT CAST(SUM(CASE WHEN EmailPromotion = 2 THEN 1 ELSE 0 END) AS REAL) * 100 / SUM(CASE WHEN PersonType = 'SC' THEN 1 ELSE 0 END) FROM Person WHERE FirstName = 'Mary'