Database Reference
In-Depth Information
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it is important to give your data flows and your sequence containers unique names that identify their
purpose. The naming convention we have chosen to give our ssis tasks is the task description followed by the task
type. For example, to fill up an authors table using a data flow task, we would name the task Fill DimAuthors Data
Flow Task. This is a very long name, but it is self-explanatory, and you seldom—if ever—have to type it in code
elsewhere.
Note
Using Precedence Constraint Arrows
In some cases, you must perform a particular operation before another can begin. You can connect different
control flow tasks using a precedence constraint arrow. These are the arrows shown in Figure
7-14
.
Precedence constraint arrows control when a task runs in relationship to another task. When two tasks do
not have a control flow arrow between them, the tasks run simultaneously. For example, looking closer, you see
that the two data flow tasks in Figure
7-15
do not have a precedence constraint arrow between them. Therefore,
they execute at the same time.
Figure 7-15.
Control flow tasks without precedence constraint arrows
When you initially drag an SSIS task to the control flow surface, you may not see the precedence constraint
arrow, just as you do not see one in Figure
7-15
, but one magically appears once you click a task. When the arrow
appears, you can click the arrow and then drag it to the other control flow task that you want to connect.
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Rules, rules, and more rules…! You cannot drag a precedence constraint arrow between tasks inside
different sequence containers. instead, you must connect the containers. Containers can connect to other containers,
and containers can connect to individual tasks, but individual tasks can only connect to other individual tasks.
Note
It is possible to create more than one precedence constraint arrow per task. After creating the first
precedence constraint arrow, click the initial task again. This causes another arrow to appear that you can then
connect to other tasks, thereby performing complex control flow scenarios (Figure
7-16
).
