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 Devart - 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 Devart - SQL toolbar.