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How do you fix no matching unique or primary key for this column list?
This error commonly occurs when you try to create a foreign key that references a table that doesn’t have a primary key. To resolve this problem, create a primary key on the referenced table. Then re-execute your command to create the foreign key.
What is primary key and foreign key?
A primary key is a column or a set of columns in a table whose values uniquely identify a row in the table. A foreign key is a column or a set of columns in a table whose values correspond to the values of the primary key in another table.
Can a table have foreign key without primary key?
A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. So in your case if you make AnotherID unique, it will be allowed.
Can a foreign key refer to a composite primary key?
The foreign key can not refer to part of composite primary key of other table. Because it is supposed to be one-to-one relationship and if you refer just part of primary-key, there might be more than one parent record available, which is neither allowed nor possible.
What is primary key foreign key unique key?
A primary key is used to ensure data in the specific column is unique. A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. 2. It uniquely identifies a record in the relational database table.
Is foreign key always primary key?
A foreign key must refer to an entire primary key, and not just part of it. Consider a Department table with a primary key of company_name + department_name. An Employee table should only refer to both attributes and not to department_name alone. Lack of foreign key indexes.
Why is there no matching unique or primary key for this column?
Error report – SQL 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.
Can a foreign key refer to a unique column?
In the above scenario, the foreign key works fine but the primary key in table t1 works only for new values. Conclusion: A foreign key must always refer to a column or columns declared as either PRIMARY KEY or UNIQUE in Oracle. Fullname etc. are not declared as unique in the parent table, and therefore you can’t reference them from the child table.
Can you create a primary key with a non-unique index?
If you create a primary key with non-unique index and NOVALIDATE option then it is possible. BUT this can lead to confusing results. Let me explain a situation. I have created a table with one column ID which has a primary key constraint with a non-unique index. Let’s create another table to reference the first table. Generate some records.
Can a column have a PK or unique key?
Columns referenced by a foreign key constraint should have a PK or unique constraint in the referenced table. This is not true for Full_Name, Nationality, Fingerprint_Template. To be honest, those FK constraints are unnecessary, remove them, and keep the FK constraint on Student_ID. Also: This is not a valid column definition.