You can join an IDoc with one or more tables in an Application Source Qualifier. An IDoc can only appear as the first object in the program flow. When you join an IDoc with more than one table, each table must have a key relationship with at least one other table above it. If a table has a key relationship with an IDoc source but has no relationship with any other table in the program flow, the Designer returns an error message when you generate the ABAP program.

When you generate SQL using ABAP join syntax, you cannot override the default join conditions between an IDoc and a table in the Join Condition tab. To override the default join condition, specify the join condition as a static filter condition for the IDoc. Enter the condition in the static filter and clear the IDoc source check box in the Join Type tab.