ABAP Keyword Documentation → ABAP Dictionary → Classic Objects in ABAP Dictionary → Database Tables → Semantic Attributes of Database Tables → Table-Specific Semantic Attributes of Database Tables → Foreign Key Dependencies
Table fields of a database table whose data type is determined using a data element can be assigned a check table. Here, the value table of any domain of the data element is used as a default value. A table field to which a check table is assigned is called a foreign key field and becomes a part of the foreign key of the table. The table itself becomes a foreign key table. The primary key of the check table is the foreign key of the foreign key table. Each key field of the check table corresponds to a field in the foreign key table. Here, the corresponding field pairs must have the same data type.
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- Fields whose data type is specified directly cannot be assigned a check table.
- As long as a database table is a check table none of its key fields can be deleted and the order of the key fields cannot be modified.
- As long as a database table is a check table its primary key can be expanded later only by appending new key fields to its end. The existing foreign keys then automatically become generic with respect to the new key fields.
- A client field cannot be inserted later in an existing check table.