Oracle Delete primary key to view primary KEY constraints and create federated primary keys _oracle

1, deletion of primary key

ALTER TABLE tablename Drop Primary_key
executes the above SQL to delete the primary key, and if it is unsuccessful,
ALTER TABLE tablename drop CONSTRAINTS COLUMN CASCADE; --delete constraint
ALTER TABLE tablename DISABLE primary_column;--Set the column that is set as the primary key invalid
DROP index index_name;--Delete primary key index

2, view primary KEY constraints

SELECT * from user_constraints WHERE constraint_type= ' P ' and table_name= ' the table name you want to see ' and Owner=user

3, creating a federated primary key

ALTER TABLE ADD CONSTRAINTS ' constraint name ' PRIMARY KEY (Column,column,...);