-- Database schema
| Customers : CustomerID [ INTEGER ] primary_key , FirstName [ TEXT ] , MiddleInitial [ TEXT ] , LastName [ TEXT ] | Employees : EmployeeID [ INTEGER ] primary_key , FirstName [ TEXT ] , MiddleInitial [ TEXT ] , LastName [ TEXT ] | Products : ProductID [ INTEGER ] primary_key , Name [ TEXT ] , Price [ REAL ] | Sales : SalesID [ INTEGER ] primary_key , SalesPersonID [ INTEGER ] Sales.SalesPersonID = Employees.EmployeeID , CustomerID [ INTEGER ] Sales.CustomerID = Customers.CustomerID , ProductID [ INTEGER ] Sales.ProductID = Products.ProductID , Quantity [ INTEGER ] |
-- -- Among all the customers who have purchased ML Bottom Bracket, identify the percentage of sales by Albert I. Ringer?

SELECT CAST(SUM(IIF(T3.FirstName = 'Albert' AND T3.MiddleInitial = 'I' AND T3.LastName = 'Ringer', 1, 0)) AS REAL) * 100 / COUNT(T2.CustomerID) FROM Products AS T1 INNER JOIN Sales AS T2 ON T1.ProductID = T2.ProductID INNER JOIN Employees AS T3 ON T2.SalesPersonID = T3.EmployeeID WHERE T1.Name = 'ML Bottom Bracket';