For two tables ‘Employees’ and ‘Sales’, if we want to get total sales done by employee with a specific employee name.
Employees table
EmployeeID, EmployeeFirstName, EmployeeLastName, EmployeeEmailID, EmployeeContactNo
Sales table
SalesID, SalesEmployeeID, SalesDate, SalesTotal
The requirement can be fulfilled by the below 2 SQL statement. What is the performance difference between these three.
SELECT COUNT(SalesTotal), SUM(SalesTotal) FROM Sales WHERE SalesEmployeeID = (SELECT EmployeeID FROM Employees WHERE EmployeeFirstName = 'GIVEN') SELECT COUNT(SalesTotal), SUM(SalesTotal) FROM Sales s INNER JOIN Employees e ON s.SalesEmployeeID = e.EmployeeID WHERE e.EmployeeFirstName = 'GIVEN' SELECT COUNT(SalesTotal), SUM(SalesTotal) FROM Sales s, Employees e WHERE s.SalesEmployeeID = e.EmployeeID AND e.EmployeeFirstName = 'GIVEN'