The CHECK clause lets you specify a condition that each row in the
table must satisfy. To satisfy the constraint, each row in the table
must make the condition either TRUE or unknown (due to a null). When
Oracle evaluates a CHECK constraint condition for a particular row,
any column names in the condition refer to the column values in that
row.
If you create multiple CHECK constraints for a column, design them
carefully so their purposes do not conflict, and do not assume any
particular order of evaluation of the conditions. Oracle does not
verify that CHECK conditions are not mutually exclusive.
See Also:
Chapter 5, "Conditions" for additional information and syntax
Restrictions on CHECK Constraints
You cannot specify a CHECK constraint for a view.
The condition of a CHECK constraint can refer to any column in the
table, but it cannot refer to columns of other tables.
CHECK constraint conditions cannot contain the following constructs:
Subqueries
Calls to the functions SYSDATE, UID, USER, or USERENV
The pseudocolumns CURRVAL, NEXTVAL, LEVEL, or ROWNUM
