Key fields

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Key fields are the subset of fields within a table for which data MUST be entered and validated before a new record can be added to the table. Failure to correctly enter data in all the key fields will prevent a new record from being added to the table.

This can be implemented in Oracle by defining all key fields (columns) as either part of the PRIMARY KEY or NOT NULL.

[edit] Example

In the below example, c1 and c2 are key fields, but c3 is not:

CREATE TABLE t1(
  c1 NUMBER       PRIMARY KEY,
  c2 VARCHAR2(30) NOT NULL,
  c3 VARCHAR2(10)
);
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