Parameter is a placeholder for a variable that contains a value of some type that is passed to a database server along with the SQL text at the query execution time. Also, parameter can hold values returned by a server after query or stored procedure execution.
You can benefit from using of parameters in the following situations:
When you execute a query multiple times with different input values
When you debug a query from your application code
Parameters are declared using the ‘@’ prefix followed by name of the parameter. Prefix is included to the name of the parameter.
SELECT Employee.* FROM HumanResources.Employee WHERE Employee.Title = @Job AND Employee.VacationHours <= @Level
@Job and @Level are parameters in this query.
When you run a query that contains parameters with empty values, you will automatically be prompted to initialize them.
To set parameter values and types, select Edit Parameters on the SQL toolbar, or press F8. In the opened Edit Parameters dialog box, set parameter type, value, and other properties.
When you execute a query with preset parameter values, you will not be automatically prompted to edit them. To edit parameters, press F8 or select Edit Parameters on the SQL toolbar.