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:
There are two types of parameters, that you can add to a query text:
Parameters are declared using : or @ prefix followed by name of the parameter.
SELECT employee.* FROM hr.employee WHERE employee.title = :job AND employee.vacation_hours <= :level
:job and :level are parameters in this query.
Unnamed parameters can be specified as ? symbol.
SELECT employee.* FROM hr.employee WHERE employee.title = ? AND employee.vacation_hours <= ?
Parameters for this query are created in the order of appearance.
When you run a query that contains parameters with empty values, you will be automatically prompted to initialize them.
To set parameter values and types click Edit Parameters on the SQL toolbar or main menu. In the Edit Parameters dialog box, set parameters’ 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.