Restrictions on Referential Constraints

You must have the REFERENCES privilege to create a referential constraint.

The following restrictions apply to the column that is specified (the referenced column) in the REFERENCES clause:

• The referenced and referencing tables must be in the same database.
• The referenced column (or set of columns) must have a unique or primary-key constraint.
• The referencing and referenced columns must be the same data type.

  (The only exception is that a referencing column must be an integer data type if the referenced column is a serial data type.)

• You cannot place a referential constraint on a BYTE or TEXT column.
• Constraints uses the collation in effect at their time of creation.
• A column-level REFERENCES clause can include only a single column name.
• Maximum number of columns in a table-level REFERENCES clause is 16.
• In Dynamic Server, the total length of the columns in a table-level REFERENCES clause cannot exceed 390 bytes.
• In Extended Parallel Server, the total length of the columns in a table-level REFERENCES clause cannot exceed 255 bytes.