Relations and Conditions

Relations and conditions are two different means of restricting the data being harvested. They may be used together or individually. The conditions are evaluated first. This means that if the conditions are not met, the relations are not evaluated.

Relations are passed to, and evaluated by, the remote system via the selected harvester. This means that relations are evaluated in different ways depending on the hasvester used and the remote system being harvested. For example, when harvesting a relational database via the ODBC Harvester, the relation is expressed as the where clause of the SQL-statement passed to the database. For more information about how relations are evaluated, please see the documentation of the different harvesters. 

Conditions are evaluated by Marshal at runtime. If, and only if, the conditions of a query node are met, the query node and its harvester will execute. This means that you may limit the execution of query node based of the resulting data of a parent query node.

To add or edit conditions, select the condition property and click on the ellipsis button. This will display the condition editor. 

You may add any number of conditions. A logical AND operator is applied between all conditions. 

Condition comparison operators
=	Equal to
!=	Not equal to
>	Greater than
>=	Greater than or equal to
<	Less than
<=	Less than or equal to
!>	Not greater than
!<	Not less than
IsNull	The data is null.
IsNullOrEmpty	The data is null or an empty string.
IsNullOrWhiteSpace	The data is null, an empty string or a string only containing white spaces characters.
IsNotNull	The data is not null.
IsNotNullOrEmpty	The data is not null or an empty string.
IsNotNullOrWhiteSpace	The data is not null, an empty string or a string only containing white spaces characters.