First normal form is a relation in which the intersection of each row and column contains one and only one value. To transform the unnormalized table (a table that contains one or more repeating groups) to first normal form, we identify and remove the repeating groups within the table. A repeating group is a set of columns that store similar information that repeats in the same table. Consider the following table, which contains the contact tracking information:


The above data structure contains a repeating group of the date and description of two conversations. The only advantage of designing the table like this is that it avoids the need for a relationship. But the disadvantages are many:

  • This structure limits the number of conversations to two, which will create problems when more than two conversations need to be stored.
  • This structure also makes it difficult to do any kind of meaningful searching using the columns, for example to locate a conversation on a specific date (here both the date columns have to be searched which will result is a clumsy SQL code).

To eliminate the repeating group, the group is moved to another table, which is then related to the parent table. The primary key of the parent table (CONTACTJD) is stored in the second table. Moving the repeating group into another table allows any number of conversations to be recorded and searched easily. The primary and foreign key relationships are defined to ensure that conversations that do not relate to a contact are not recorded.



In summary, every table should have a primary key of repeating groups should appear in its own table. When these criteria are satisfied, we say that the first normal form is achieved.

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