Unique constraint on valid_to and valid_from dates

Question

Suppose I have a table:
create table test (name varchar2(40), valid_from date, valid_to date);
insert into test values ('fred', to_date('01/04/2008', 'dd/mm/yyyy'), to_date('01/04/2008', 'dd/mm/yyyy');
insert into test values ('fred', to_date('04/04/2008', 'dd/mm/yyyy'), to_date('06/04/2008', 'dd/mm/yyyy');
insert into test values ('fred', to_date('08/04/2008', 'dd/mm/yyyy'), to_date('09/04/2008', 'dd/mm/yyyy');How can I enforce uniqueness such that at any one point in time, only one row exists in the table for each name?
eg. insert into test values ('fred', to_date('02/04/2008', 'dd/mm/yyyy'), to_date('03/04/2008', 'dd/mm/yyyy'); -- success!
insert into test values ('fred', to_date('02/04/2008', 'dd/mm/yyyy'), to_date('05/04/2008', 'dd/mm/yyyy'); -- fail!
insert into test values ('fred', to_date('01/04/2008', 'dd/mm/yyyy'), to_date('03/04/2008', 'dd/mm/yyyy'); -- fail!
insert into test values ('fred', to_date('05/04/2008', 'dd/mm/yyyy'), to_date('05/04/2008', 'dd/mm/yyyy'); -- fail!
insert into test values ('fred', to_date('07/04/2008', 'dd/mm/yyyy'), to_date('11/04/2008', 'dd/mm/yyyy'); -- fail!Is there a method using fbi's or unique constraints? I'd really rather avoid using triggers and pl/sql if I can, but I can't think of a way...
Message was edited by:
Boneist
Added some extra test conditions

Answer 1

How about this pair of indexes:
CREATE UNIQUE INDEX test_fromdate_idx ON test(name,valid_from);
CREATE UNIQUE INDEX test_todate_idx ON test(name,valid_to);Here is the test:
SQL> create table test (name varchar2(40), valid_from date, valid_to date);
Table created.
SQL> insert into test values ('fred', to_date('01/04/2008', 'dd/mm/yyyy'), to_date('01/04/2008', 'dd/mm/yyyy'));
1 row created.
SQL> insert into test values ('fred', to_date('04/04/2008', 'dd/mm/yyyy'), to_date('06/04/2008', 'dd/mm/yyyy'));
1 row created.
SQL> insert into test values ('fred', to_date('08/04/2008', 'dd/mm/yyyy'), to_date('09/04/2008', 'dd/mm/yyyy'));
1 row created.
SQL> CREATE UNIQUE INDEX test_fromdate_idx ON test(name,valid_from);
Index created.
SQL> CREATE UNIQUE INDEX test_todate_idx ON test(name,valid_to);
Index created.
SQL> insert into test values ('fred', to_date('02/04/2008', 'dd/mm/yyyy'), to_date('03/04/2008', 'dd/mm/yyyy'));
1 row created.
SQL> insert into test values ('fred', to_date('02/04/2008', 'dd/mm/yyyy'), to_date('05/04/2008', 'dd/mm/yyyy'));
insert into test values ('fred', to_date('02/04/2008', 'dd/mm/yyyy'), to_date('05/04/2008', 'dd/mm/yyyy'))
ERROR at line 1:
ORA-00001: unique constraint (TEST_USER.TEST_FROMDATE_IDX) violated
SQL> insert into test values ('fred', to_date('01/04/2008', 'dd/mm/yyyy'), to_date('03/04/2008', 'dd/mm/yyyy'));
insert into test values ('fred', to_date('01/04/2008', 'dd/mm/yyyy'), to_date('03/04/2008', 'dd/mm/yyyy'))
ERROR at line 1:
ORA-00001: unique constraint (TEST_USER.TEST_FROMDATE_IDX) violated
SQL> spool off;Hope this helps!