I have a foreign constraint as below. This was created like three years ago. All the data that are created after this constraint are valid but the backlog data (data before three years) are not valid. Toad shows this constraint as 'Not Validated'
ALTER TABLE ISSUES ADD (
CONSTRAINT FK_CLIENT
FOREIGN KEY (CLIENT)
REFERENCES REPORTERS(USERID)
DEFERRABLE INITIALLY DEFERRED);
Today i fixed all the backlog data and now this constraint will hold good both for existing as well as new data. But how will i make the constraint as 'Validated'.
Is there any way to 're-validate' a foreign constraint?
You should be able to:
ALTER TABLE issues ENABLE VALIDATE CONSTRAINT fk_client;
Related
Sorry, I don't well English.
CREATE TABLE Reservation(
tno NUMBER,
sno NUMBER,
cno NUMBER,
seat_no NUMBER,
Res_Date DATE,
CONSTRAINT FK_RES_TNO FOREIGN KEY (tno) REFERENCES Theater(tno),
CONSTRAINT FK_RES_SNO FOREIGN KEY (sno) REFERENCES Screen(sno),
CONSTRAINT FK_RES_CNO FOREIGN KEY (cno) REFERENCES T_Customer(cno),
CONSTRAINT PK_RESERVATION PRIMARY KEY (tno,sno,cno)
--CONSTRAINT RES_UNIQUE UNIQUE (cno)
);
I Write Oracle Table.
But throw me Error "ORA-02270"
I don't know come to me this message.
Could you tell me some advise?
There would be multiple reasons for having this error,
You may have same primary key already, which might be disabled
Composite primary key in the table may not provide you the unique (this error many happen only when the table is ALTERED, since its new table, this logical check can be ignored)
I'm creating a couple of Tables for an assignment.
So I created a Gardener Table and an Offering Table, with all the appropriate data types and NULL statuses, as well as the Primary Key constraint for each. In the Gardener table I've included offeringID, and vice versa.
When I try to add Foreign Key constraint offeringID to the Gardener Table I get an error.
After checking online, I realized I had forgotten to make offeringID and gardenerID in each other's tables UNIQUE, hence I altered table to add uniqueness.
Tried adding Foreign Key constraint and I get the same error. I reckon I may be understanding something wrongly, but I can't seem to put my finger on it.
Create Table Gardener
(gardenerID NUMBER(10) NOT NULL,
offeringID NUMBER(10) NOT NULL,
CONSTRAINT gardener_pk PRIMARY KEY(gardenerID)
);
Create Table Offering
(offeringID NUMBER(10) NOT NULL,
gardenerID NUMBER(10) NOT NULL,
CONSTRAINT offering_pk PRIMARY KEY(offeringID)
);
Alter Table Gardener
add CONSTRAINT offering_fk FOREIGN KEY(offeringID)
REFERENCES Offering(offeringID);
Alter Table Gardener
add Unique(offeringID);
Alter Table Offering
add Unique(gardenerID);
This is the error:
ORA-02270: no matching unique or primary key for this column-list
02270. 00000 - "no matching unique or primary key for this column-list"
Cause: A REFERENCES clause in a CREATE/ALTER TABLE statement gives a column-list
for which there is no matching unique or primary key constraint in the referenced table.
Like, I still don't get it. Isn't offeringID a Primary Key hence pointing to it from Gardener shouldn't be an issue still?
Since you're trying to add a a foreign key constraint for offering.offeringID column within the Gardener table, whereas that column has no unique/primary key key when you try to add a foreign key. i.e. operation stops at the 3rd command.
So, just exchange the order of commands as :
Alter Table Gardener
add Unique(offeringID); -- should be prior to the below command
Alter Table Gardener
add CONSTRAINT offering_fk FOREIGN KEY(offeringID)
REFERENCES Offering(offeringID);
Demo
I have two tables with a one-to-one relationship (and relationship is mandatory from one side only). As follows:
create table PRS (
id number(18) not null,
common_code varchar2(10),
constraint pk_prs primary key (id));
create table RLP {
id number(18),
spec_code varchar2(20),
constraint pk_rlp primary key (id),
constraint fk_rlp_prs foreign key (id) references prs(id) on delete cascade);
So the problem is when inserting a record in RLP at least one of common_code or spec_code must have value.
Is it possible to enforce this constraint using a constraint or the only solution is having a trigger?
It seems there is no way to create a constraint on two tables, and the only solution is to create a trigger to throw an exception on desired situation.
I'm a bit confused over when I should use a primary or foreign key. I have two tables, and in both of them, some of the columns reference columns that are primary keys in other tables.
Here they are:
CREATE TABLE roles (
movie_id NUMBER(10,0) NOT NULL REFERENCES movies(movie_id),
actor_id NUMBER(10,0) NOT NULL REFERENCES actors(actor_id),
movie_description VARCHAR2(50),
salary NUMBER(10),
CONSTRAINT pk_roles PRIMARY KEY (movie_id, actor_id)
);
CREATE TABLE profits (
movie_id NUMBER(10,0) NOT NULL,
gross_profit NUMBER(9) NOT NULL,
net_profit NUMBER(9) NOT NULL,
CONSTRAINT fk_profits FOREIGN KEY (movie_id) REFERENCES movies(movie_id) ON DELETE CASCADE
);
In the first table I have made a composite primary key from teh two columns that reference columns in other tables. Those columns happen to be primary keys in their respective tables.
In the second table, I've made a foreign key again referencing a primary key in anther table. But what is best practice? Should the key in the first table also be a foreign key since it references primary keys in other tables?
Primary key constraints and unique constraints prevent duplicate rows. Duplicate rows not only waste space, they make it harder to get meaningful answers from your database.
Foreign key constraints restrict values to those that exist in another table. The target of a foreign key constraint is commonly a primary key, but it could be any column(s) that have a unique constraint.
Every table should have a primary key constraint. If the column(s) that make up the primary key also require a foreign key constraint, add the foreign key constraint as well.
Your table "roles" is fine, as far as implementing primary key constraints and foreign key constraints. But "profits" needs a primary key.
To your Question "Should the key in the first table also be a foreign key since it references primary keys in other tables?"
There is no simple answer, as it heavily depends on type of planned usage of data and database being used. If you need a simple answer, yes it is a good idea. Below is the longer version.
Pros :
It helps keep your data clean.
Based on how database is planned to be used and which database you are using, some databases, tend to optimize joins better, if Foreign keys are defined for joins upfront.
Cons :
If you plan to bulk load into your tables frequently, then FK constraints tend to slow down your loads, if that is the case, some databases allow you to define soft constraints, which are only used for query optimization purposes, but are not verified during loads.
I've just started a new project and I am confronted with a production application Oracle 10g database that has just 3 foreign key constraints. I am not used to seeing databases with no foreign key constraints. I am guessing that there may be some performance/concurrency considerations to not using FKs. The reason is that in the logical database schema the architect has specified all the relationships, but these relationships are not implemented in the database as Foreign Key constraints.
Question: I read that I can define a Foreign Key Constraint with RELY NOVALIDATE that will not impact performance. Is it worth while to define RELY FK constraints on this database just so that the relationship can be easily seen? this application is not built using ORM, is it really worth while to do without foreign keys?
The database is denormalised with example below
Table 1 : FINProduct(ID (number), Description(varchar(5)), FINproductCode(varchar(10))...)
Table 2: FINProductCode(ID (number, FINproductCode(varchar(10)) , LastUpdated(datetime)...)
So instead of having a relationship between Tables 1 and 2 the FINproductCode column is just replicated in table 1.
It's too early to drink but I think i need one!
I would be very wary about assuming that the absence of foreign key constraints was a reasoned response to performance issues. There is an overhead to enforcing a foreign key constraint (particularly where appropriate indexes are missing) but it is incredibly unlikely that your application can validate the constraint more efficiently than Oracle can. So the question really is whether you want the small overhead of foreign key constraints or the near certainty that you will get invalid data inserted into the database. It would be extremely unlikely that this is a trade-off that you want to make-- I've yet to meet a business user that would be happy to capture incorrect and incomprehensible data even if doing so was a bit faster than capturing correct data.
Unless there is substantially more background, I would tend to create all the missing foreign key constraints. Creating RELY NOVALIDATE constraints is possible but it defeats the major benefit of foreign key constraints-- preventing invalid data from entering the database in the first place.
It depends on whether you want to add the FK only for documentation purposes or whether you want to prevent future INSERTs/UPDATEs with an invalid FK value.
If you want it only for documentation purposes, I'd create the FK constraint with RELY NOVALIDATE and DISABLE it afterwards - otherwise, Oracle will check it for future INSERTs / UPDATEs.
However: DON'T DO THIS UNLESS YOU ABSOLUTELY NEED IT!
I agree with Justin Cave: In most cases, you should just add "plain" FK constraints - this way, you can ensure that your existing data is correct.
I would try to create the constraints and report violations into a exception table. Fix the data and enable the constraint.
Create some test data
create table parent (pk integer
,data varchar2(1)
,CONSTRAINT PARENT_PK PRIMARY KEY (PK) ENABLE );
create table child (pk integer
,pk_parent integer
,data varchar2(1)
,CONSTRAINT CHILD_PK PRIMARY KEY (PK) ENABLE );
insert into parent values (1,'a');
insert into parent values (2,'b');
insert into child values (1,1,'a');
insert into child values (2,2,'b');
insert into child values (3,3,'c');
Create a foreign key constraint:
alter table child add constraint fk_parent foreign key(pk_parent) references parent(pk);
SQL Error: ORA-02298: Kan (ROB.FK_PARENT) niet valideren - bovenliggende sleutels zijn niet gevonden.
02298. 00000 - "cannot validate (%s.%s) - parent keys not found"
*Cause: an alter table validating constraint failed because the table has
child records.
*Action: Obvious
Create the foreign key with 'enable novalidate' option
alter table child add constraint fk_parent foreign key(pk_parent) references parent(pk) enable novalidate;
table CHILD altered.
insert into child values (4,4,'c');
SQL Error: ORA-02291: Integriteitsbeperking (ROB.FK_PARENT) is geschonden - bovenliggende sleutel is niet gevonden.
02291. 00000 - "integrity constraint (%s.%s) violated - parent key not found"
*Cause: A foreign key value has no matching primary key value.
*Action: Delete the foreign key or add a matching primary key.
No new data violating the FK can be inserted.
Now let's fix the data already in the table that violates the FK constraint
Create an exceptions table and try to enable the constraint:
create table exceptions(row_id rowid,
owner varchar2(30),
table_name varchar2(30),
constraint varchar2(30));
ALTER TABLE child ENABLE constraint fk_parent EXCEPTIONS INTO EXCEPTIONS;
Error report:
SQL Error: ORA-02298: Kan (ROB.FK_PARENT) niet valideren - bovenliggende sleutels zijn niet gevonden.
02298. 00000 - "cannot validate (%s.%s) - parent keys not found"
*Cause: an alter table validating constraint failed because the table has
child records.
*Action: Obvious
Check the exceptions table for problems:
select * from exceptions;
ROW_ID OWNER TABLE_NAME CONSTRAINT
------ ------------------------------ ------------------------------ ------------------------------
AABA78 ROB CHILD FK_PARENT
AAFAAA
Ow9AAC
select * from child where rowid = 'AABA78AAFAAAOw9AAC';
Fix the problem
delete from child where pk = 3;
1 rows deleted.
ALTER TABLE child ENABLE constraint fk_parent EXCEPTIONS INTO EXCEPTIONS;
table CHILD altered.
Constraint enabled and data correct