What is the issue when attempting to make a table with a PRIMARY KEY restriction in Oracle SQL?

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One common issue with creating a table with a PRIMARY KEY restriction in Oracle SQL is that the primary key column must not contain any duplicates or null values. If there are existing rows with duplicate or null values in the column that is being designated as the primary key, the table creation will fail. Additionally, if another table has a foreign key constraint referencing the primary key of the table being created, the table creation may fail if the referenced primary key does not exist.