Database Reference
In-Depth Information
Figure 7-19.
Configuring a precedence constraint to use an expression
Figure
7-19
also shows the “Multiple constraints” area containing radio buttons that allow you to configure a
constraint to work in conjunction with other constraints on the same task. When a control flow task contains two
or more constraints, as in Figure
7-16
, you can determine whether just one or all constraints are required to be
true before moving to the next task.
■
You may notice that the expression in Figure
7-19
uses syntax similar to C#. At other times, you may see
syntax that is more like sQL or perhaps Visual Basic. This is not C# but rather ssis's own expression language.
Microsoft has published updates to this language for each of the last four versions of sQL server.
You can find more about this language by searching the web using the keywords “ssis Expression Reference.”
Here is an example page that was available at the time of this writing:
Note
SSIS Variables
In Figure
7-19
we use a custom SSIS variable called
@RowCount
. The intended purpose of this variable is to
determine whether there are zero rows of data found in a given table. If this is true, a particular action is
performed or avoided.
