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How do you add multiple foreign key constraints?
3 Answers. The second code block from your question: ALTER TABLE ORDERS ADD FOREIGN KEY (customer_sid) REFERENCES CUSTOMER(SID), ADD FOREIGN KEY (customer_sid2) REFERENCES CUSTOMER(SID2); will take care of what you are trying to do.
Can you have multiple foreign key?
A table may have multiple foreign keys, and each foreign key can have a different parent table. Each foreign key is enforced independently by the database system.
How do I create a FOREIGN KEY constraint in MySQL?
After creating a table, if we want to add a foreign key to an existing table, we need to execute the ALTER TABLE statement as below:
- ALTER TABLE Contact ADD INDEX par_ind ( Person_Id );
- ALTER TABLE Contact ADD CONSTRAINT fk_person.
- FOREIGN KEY ( Person_Id ) REFERENCES Person ( ID ) ON DELETE CASCADE ON UPDATE RESTRICT;
How do you disable a FOREIGN KEY constraint?
To disable a foreign key constraint for INSERT and UPDATE statements In Object Explorer, expand the table with the constraint and then expand the Keys folder. Right-click the constraint and select Modify. In the grid under Table Designer, click Enforce Foreign Key Constraint and select No from the drop-down menu. Click Close.
What are the primary key and foreign key constraints?
Primary and Foreign key constraints are and what they are used for: Primary Key: A primary key is a field or combination of fields that uniquely identify a record in a table, so that an individual record can be located without confusion.. Foreign Key: A foreign key (sometimes called a referencing key) is a key used to link two tables together.
How do you add foreign keys to a table?
After naming your constraint, add the words FOREIGN KEY to specify that it is a foreign key constraint. Then, open brackets and add in the name of the column in this table that will be the foreign key. Then, close the brackets. Next, add the word REFERENCES, then the name of the other table you’re referring to.
How to modify an existing check constraint?
right-click the table containing the check constraint and select Design.