The WHERE clause specifies how the data being retrieved must be constrained.
The syntax is as following:
An expression for which the value always equals true. Expressions consist of simple comparisons using operators, functions, keywords or system variables.
SELECT FirstName FROM Sales.Customer WHERE LastName = 'Jansen'
This query retrieves all customers whose name is equal to ‘Jansen’.
SELECT FirstName FROM Sales.Customer INNER JOIN Sales.Customer/Sales.Customer_Address/Sales.Address WHERE Sales.Address/City = 'Rotterdam'
This query retrieves all customers who live in ‘Rotterdam’.