The WHERE clause specifies how the data being retrieved must be constrained.
The syntax is as following:
This query retrieves all customers whose name is equal to ‘Jansen’:
SELECT FirstName FROM Sales.Customer WHERE LastName = 'Jansen'
This query retrieves all customers who live in ‘Rotterdam’:
SELECT FirstName FROM Sales.Customer INNER JOIN Sales.Customer/Sales.Customer_Address/Sales.Address WHERE Sales.Address/LastName = 'Rotterdam'