What proportion of sales orders are made from the United Kingdom?
proportion = DIVIDE(SUM(Name = 'UK')), (COUNT(SalesOrderID))) as count;
SELECT CAST(SUM(CASE WHEN T2.Name = 'United Kingdom' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.SalesOrderID) FROM SalesOrderHeader AS T1 INNER JOIN SalesTerritory AS T2 ON T1.TerritoryID = T2.TerritoryID