Second Normal Form

For a table to be in Second Normal Form, every non-key field must depend on the entire primary key, not on part of a composite primary key. If a database has only single-field primary keys, it is automatically in Second Normal Form.

In Figure 6-3, the primary key is a composite key on emp_num and dept_no. But the value of dept_name depends only on dept_no, not on the entire primary key.

Figure 6-3: A table that violates Second Normal Form

To normalize this table, move dept_name to a second table, as shown in Figure 6-4.

Figure 6-4: Correcting Second Normal Form violations by creating two tables