Friday, September 23, 2016

Normalization and First Normal Form

  • ·         The outcome of the first step of database normalization. 1NF eliminates repeating groups by putting each into a separate table and connecting them with a 1:M relationship – First Normal Form ( 1NF)
  • ·         A series of steps followed to obtain a database design that allows for efficient access and storage of data in a relational database. These steps reduce data redundancy and the chances of data be-coming inconsistent. - Normalization

1. When checking a database model for first normal form, what are you doing exactly?
Check entities for multi-valued attributes. Verifying that each entity contains attributes that are appropriate for it; insuring that the entity has a UID; checking each attribute against its UID and verifying that the attribute only contains a single value.

2. What is the rule of 1NF in the normalization process?
First Normal Form requires that there be no multi-valued attributes and no repeating groups. To check for First Normal Form, validate that each attribute has a single value for each instance of the entity.
  • ·         identify the related data parts (attributes) and place them together in one entity; if multiple entities exist, attributes should be listed one time only and in the best possible location
  • ·         identify the UID of the entity
  • ·         remove any attribute that contains repeating groups (multiple values) and place it in its own entity; create a 1:M relationship between the two entities

3. Check to see if each ERD is in 1NF. If not, make the necessary changes to correct it.

Suggestion: passenger is multi-valued. A passenger rides a bus, he comes out of bus and go in another bus, at same time he is in single bus. (I don’t see passenger must ride bus, he may ride anything else too, so dotted on passenger side also)


Suggestion: dormitory may have multiple residents. Resident may live in dormitory or something special. Dormitory has multiple beds to accommodate many residents.


Suggestion: 1NF OK here.


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