A rough understanding of relational database paradigm

A cursory look at the introduction of relational database paradigm, simply record your understanding

The first paradigm: refers to the attribute to atomic, that is, the attribute can not be split again. For example, a person table, where a field is a personal information p_info, this personal information can be re-divided into name, gender, age three fields. Then person this table does not reach the first paradigm, the personal information should be broken down into the name, gender, age before the first paradigm.

The second paradigm: when the first paradigm is reached, the non-primary attribute full function relies on the primary attribute, just like a primary key is set in the table, and the property outside the primary key is completely dependent on the primary attribute. A full function dependency means x determines y, but any subset of x cannot determine Y. Even if the primary key contains only one field, it must have reached the full function dependency, and if the primary key is a composite primary key containing more than one field, then it is required to remove any of the fields from the composite primary key and not be the primary key for the table. This is similar to the relationship between the candidate key and the super-key.

The third paradigm: when the second paradigm is reached, the non-principal property does not pass the function dependent on the primary attribute. The transfer function relies on x→y,y→z and y-/->x, that is, X determines that the y,y determines z and y cannot determine X, which means that the Z-pass function depends on X, and if y can determine x, then the z-direct function depends on X.

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A rough understanding of relational database paradigm