How to resolve ora 02270 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 foreign key constraint?

A foreign key constraint specifies that the key can only contain values that are in the referenced primary key, and thus ensures the referential integrity of data that is joined on the two keys. You can identify a table’s foreign key when you create the table, or in an existing table with ALTER TABLE .

How do I drop a constraint in Oracle?

Drop Unique Constraint The syntax for dropping a unique constraint in Oracle is: ALTER TABLE table_name DROP CONSTRAINT constraint_name; table_name.

What does no matching unique or primary key for this column list?

If you see this error, it simply means that the target table (the table name following the REFERENCES keyword) lacks a constraint, either a primary key or a unique key defined on the columns listed inside the parentheses.

What is All_cons_columns?

ALL_CONS_COLUMNS describes columns that are accessible to the current user and that are specified in constraints. Related Views. DBA_CONS_COLUMNS describes all columns in the database that are specified in constraints.

Is primary key unique Oracle?

Introduction to the primary key A primary key value must be unique within the entire table. A primary key value should not be changed over time.

What is unique key and primary key?

A primary key is a column of table which uniquely identifies each tuple (row) in that table. Primary key enforces integrity constraints to the table. Unique key constraints also identifies an individual tuple uniquely in a relation or table. A table can have more than one unique key unlike primary key.

How do you fix Ora 00001 unique constraint violated?

There are a few solutions to the “ORA-00001 unique constraint violated” error:

1. Change your SQL so that the unique constraint is not violated.
2. Change the constraint to allow for duplicate values.
3. Drop the constraint from the column.
4. Disable the unique constraint.

Can we drop unique index in Oracle?

How to drop unique index in oracle. you can’t drop any implicitly created index, such as those created by defining a UNIQUE key constraint or primary key constaint on a table, with the drop index command. If you try to do so it will throw an error.