Written by Ravi Prakash
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Friday, 29 June 2007
Category MS Access 2007 - Queries.
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| General Information |
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Database normalization
Relationships in Access 2007
Create queries
Open a recently used database
Open a database through Microsoft Office Access button
Close a database
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| Database normalization |
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Database normalization is the process to organize the data of a data base. It includes the creation of tables and the establishment of relations among them according to designed rules by eliminating the incoherent redundancy and dependencies. |
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Redundancy data waste disk space and create maintenance problems. If there is to change data that exist in more of a place, they are due to change exactly
of the same form in all his locations. A change in the direction of a client is much easier to implement if the data only store in the table Clients and
not in some other place of the data base. |
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Microsoft Access 2007 uses the relational model for the database management which is based on the logic of predicates where the data is represented by
mathematical n-ary relations. Each relation is represented by the composition of fields stored in tables that represent these n-ary relations. |
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To transform a database in a relational database there are several normalization forms to apply: |
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| First normal form |
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| 1) Eliminate the repeated groups of the individual tables. |
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| 2) Create an independent table for each related data set. |
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| 3) Identify each data set related with a primary key. |
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| Second normal form |
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| 4) Create independent tables for sets of values that are applied to several records. |
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| 5) Relate these tables to an external key. |
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| Third Normal form |
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| 6) Eliminate the fields that do not depend on the key. |
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| Record values that are not part of the key of that record do not belong to the table. In general, whenever the content of a group of fields can be
applied to more of an only registry of the table, it considers placing these fields in an independent table. |
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| There are two additional normal forms (fourth and fifth) but both are rarely used. |
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| Relationships in Access 2007 |
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| 7) Open TutorialDB. |
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| 8) Click on Database Tools and select Relationships. Remember that the database must be normalized before. |
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| Illustration 1: Normalize the database and create relationships between tables and data. Click here to view larger image. |
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| A blank screen will appear. You must add tables. |
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| 9) Right click on the empty screen and select the Show table menu item. |
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| Illustration 2: Normalize the database and create relationships between tables and data. Click here to view larger image. |
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