I need to change multiple tables to foreign keys. I have used the command
ALTER TABLE financial_transactions
ADD FOREIGN KEY (item_rental_id) REFERENCES transaction_id(item_rental_id);
The table name was financial_transactions and the column name was item_rental_id. It gives me an error saying:
Foreign key 'FK__financial__item___46E78A0C' references invalid table 'transaction_id'.
How do I resolve this?
Yes, this is a correct script to create a foreign key
ALTER TABLE financial_transactions
ADD FOREIGN KEY (item_rental_id) REFERENCES customer_rentals(item_rental_id);
However, if you are trying to add a foreign key constraint on a table with data already in it, you have to make sure that the item_rental_id in financial_transactions table are also in the customer_rentals table. Otherwise, you will have a referential integrity error.
To illustrate:
CREATE TABLE customer_rentals_1
(item_rental_id INT,
PRIMARY KEY (item_rental_id)
);
CREATE TABLE financial_transactions_1
(transaction_id INT,
item_rental_id INT,
PRIMARY KEY (transaction_id)
);
ALTER TABLE financial_transactions_1
ADD FOREIGN KEY (item_rental_id) REFERENCES customer_rentals_1(item_rental_id);
The scripts above will run successfully.
CREATE TABLE customer_rentals_2
(item_rental_id INT,
PRIMARY KEY (item_rental_id)
);
CREATE TABLE financial_transactions_2
(transaction_id INT,
item_rental_id INT,
PRIMARY KEY (transaction_id)
);
INSERT INTO financial_transactions_2
VALUES (1000, 9999);
ALTER TABLE financial_transactions_2
ADD FOREIGN KEY (item_rental_id) REFERENCES customer_rentals_2(item_rental_id);
But, this will have the following error since item_rental_id 9999 is not present in customer_rentals_2 table
Msg 547, Level 16, State 0, Line 31
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK__financial__item___76969D2E". The conflict occurred in database "TESTDB", table "dbo.customer_rentals_2", column 'item_rental_id'.
You have to give second table name
both way can do it
1. Add reference without name
ALTER TABLE financial_transactions
ADD FOREIGN KEY (item_rental_id) REFERENCES customer_rentals(item_rental_id);
2.Add reference with a name
ALTER TABLE financial_transactions
ADD CONSTRAINT FK_Financial_Transactions_Customer_Rental_Item_Rental_ID
FOREIGN KEY (item_rental_id) REFERENCES Customer_rentals(item_rental_id);
Related
My problem is that i have two tables with each table having a foreign key to the other table.
Each time , i execute the SQL file containing the creation of the two tables, it gives me an error that he doesn't find the other table. I'm working with sqlplus to execute the sql file.
Here's an example of SQL file i tried with :
create table A(
Age number(3),
name number(3) constraint A_FK references B(name))
/
create table B(
Age number(3) constraint B_FK references A(Age),
name number(3))
And even if i reverse the order, it gives the same error.
Thanks for help.
This is a problem of cycles in foreign keys. One method is to add all foreign keys after table creation (as I think the other answers propose).
You can also just do that for the first table:
create table A (
Age number(3) primary key,
name number(3)
);
create table B (
name number(3) primary key,
Age number(3),
constraint B_FK foreign key (age) references A(Age)
);
alter table B add constraint A_FK foreign key (name) references B(name);
Here is a db<>fiddle.
Notes:
Foreign keys should reference primary keys, so I added that declaration as well.
I recommend making the primary key the first column in the table.
You can also define the constraint inline for one of the tables (i.e. age number(3) constraint b_fk references a(age)).
The table column(s) that is referred by a foreign key must exist at the time when the constraint is created. Since you have some kind of cyclic reference between the tables, you need to do this in three steps:
first create one table without the foreign key
create the second table (with its foreign key)
finally add the foreign key to the first table with an alter table statement
You also need the referred column to have a unique or primary key constraint set up, otherwise you would get error ORA-02270: no matching unique or primary key for this column-list.
create table A(
age number(3) primary key,
name number(3)
);
create table B(
age number(3) constraint B_FK references A(Age),
name number(3) primary key
);
alter table A add constraint A_FK foreign key (name) references B(name);
Demo on DB Fiddle
Side note: I am quite suspicious about your sample structure, but this could be because your oversimplified it in the question.
It fails because the reference table doesn't exist yet.
Create the tables without the key first. Then drop one and recreated it with the reference. Then drop the 2nd and recreate it with the reference.
Create table first and then ADD the CONSTRAINT
ALTER TABLE A
ADD FOREIGN KEY (name) REFERENCES B(name);
ALTER TABLE B
ADD FOREIGN KEY (age) REFERENCES A(age);
alter table course_relation
add foreign key (offered_By)
references department_relation(dept_cd)
alter table department_relation
add foreign key(hod)
references staff_relation(staff_no)
alter table staff_relation
add foreign key (dept_cd)
references department_relation(dept_cd)
//the third para doesn't work but the first two works fine
error message:
Msg 547, Level 16, State 0, Line 10 The ALTER TABLE statement
conflicted with the FOREIGN KEY constraint
"FK__staff_rela__dept__1BC821DD". The conflict occurred in database
"Royal_Poly_DB", table "dbo.Department_Relation", column 'Dept_Cd'.
You can't create circular foreign key references.
In this Statement
alter table department_relation
add foreign key(hod)
references staff_relation(staff_no)
In this alter query you create foreign key reference in 'department_relation' from 'staff_relation' table.
alter table staff_relation
add foreign key (dept_cd)
references department_relation(dept_cd)
In this alter query you create foreign key reference in 'staff_relation' from 'department_relation' table.
This is circular dependency of foreign key and it is allowed.
I am trying to add foreign key to my existing column using below query
ALTER TABLE Sub_Category_Master
ADD FOREIGN KEY (Category_ID) REFERENCES Category_Master(Category_ID)
but I'm getting an error
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK__Sub_Categ__Categ__5812160E". The conflict occurred in database "shaadikarbefikar_new", table "shaadikarbefikar.Category_Master", column 'Category_ID'.
Well, the error clearly tells you that Category_ID in your Sub_Category_Master table contains some values that are not present in Category_Master (column Category_ID). But that's exactly the point of having a foreign key constraint - making sure your child table (Sub_Category_Master) only uses defined values from its parent table.
Therefore, you must fix those "voodoo" values first, before you're able to establish this foreign key relationship. I would also strongly recommend to explicitly name that constraint yourself, to avoid those system-generated, but not really very useful constraint names like FK__Sub_Categ__Categ__5812160E:
ALTER TABLE Sub_Category_Master
ADD CONSTRAINT FK_SubCategoryMaster_CategoryMaster
FOREIGN KEY (Category_ID) REFERENCES Category_Master(Category_ID)
ALTER TABLE Sub_Category_Master
ADD CONSTRAINT FKSub_Category_Master_Category_ID FOREIGN KEY (Category_ID)
REFERENCES Category_Master(Category_ID);
CREATE TABLE Orders
(
OrderID int NOT NULL,
OrderNumber int NOT NULL,
PersonID int,
PRIMARY KEY (OrderID),
CONSTRAINT FK_PersonOrder
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);
i want to add to a primary key in one table a references to the primary key of another table.
my code:
CREATE TABLE[payment]
(ID int Primary key)
CREATE TABLE [tab]
(ID int Primary key references tab2(ID))
Alter Table payment
alter column ID
ADD constraint fk_payment
references tab(ID)
i get the error that the syntax near constraint is wrong, but i don't know what to change
because of the not changeable order of the table Alter table is the only option. to reference from one table to the other doesn't work cause I've references from that table to another one already.
i need two one-to-one-relations from one table to another
If you want to add a FK constraint, just use this code:
ALTER TABLE dbo.payment
ADD CONSTRAINT fk_payment
FOREIGN KEY(ID) REFERENCES dbo.tab(ID)
You don't need to alter the column or table - just add the constraint
I had to write the SQL to create the tables, attributes, and primary & foreign keys in this ERD:
http://imgur.com/VYZbwr6
In the table 'Financial_Transactions' in the ERD there is a attribute called 'previous_transaction_id' and another attribute called 'transaction_id'. In this table 'previous_transaction_id' is a Foreign Key for this table in addition to being an attribute. It references the last 'transaction_id' in the table.
Here is my SQL for the 'financial_transactions' table:
CREATE TABLE financial_transactions(
transaction_id int IDENTITY(1,1) NOT NULL,
account_id int NOT NULL,
item_rental_id int NOT NULL,
previous_transaction_id int,
transaction_type_code int NOT NULL,
transaction_date date NOT NULL,
transaction_amount money NOT NULL,
transaction_comment varchar(512) NOT NULL);
ALTER TABLE financial_transactions ADD CONSTRAINT pk_financial_transactions PRIMARY KEY (transaction_id);
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_accounts FOREIGN KEY(account_id)
REFERENCES accounts (account_id);
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_customer_rentals FOREIGN KEY(item_rental_id)
REFERENCES customer_rentals (item_rental_id);
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_financial_transactions FOREIGN KEY(previous_transaction_id)
REFERENCES financial_transactions (previous_transaction_id);
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_transaction_types FOREIGN KEY(transaction_type_code)
REFERENCES transaction_types (transaction_type_code);
When I run my SQL (includes statements for each table in the script) I get these errors:
"Msg 1776, Level 16, State 0, Line 87
There are no primary or candidate keys in the referenced table 'financial_transactions' that match the referencing column list in the foreign key 'fk_financial_transactions_financial_transactions'.
Msg 1750, Level 16, State 0, Line 87
Could not create constraint. See previous errors."
All other statements execute normally.
What am I doing wrong?
*I used this statement originally under CREATE TABLE: previous_transaction_id int NOT NULL,
However, it resulted in the same error and when searching I saw a similar question that was fixed by removing the NOT NULL.
Here
ALTER TABLE financial_transactions ADD CONSTRAINT
fk_financial_transactions_financial_transactions
FOREIGN KEY(previous_transaction_id)
REFERENCES financial_transactions (previous_transaction_id);
You have a column referencing itself. Was that your intent or did you want to reference the transaction_id?
There is nothing wrong with defining a foreign key to the same table but you have a column referencing itself.
Try replacing:
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_financial_transactions FOREIGN KEY(previous_transaction_id)
REFERENCES financial_transactions (previous_transaction_id);
With:
ALTER TABLE financial_transactions ADD CONSTRAINT fk_financial_transactions_financial_transactions FOREIGN KEY(previous_transaction_id)
REFERENCES financial_transactions (transaction_id);