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Slide 12.5: Tables and relations Slide 12.7: The relational rules (cont.) Home         Print version

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The Relational Rules

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There are a couple of rules needed to be followed by the relational databases.

Rule 1: First Normal Form Rule
A table that has no multi-valued attributes (repeating fields) and no internal structure (record) is said to be in first normal form.

• No internal structure: A column named ename having three components, ename.fname, ename.lname, and ename.mi, is not allowed since this assumes a structure in column values that is not permitted in the first normal form.


• No multi-value attributes: Below shows an example of how to solve the problem of multi-value attributes:
  
  

  employee eid ename position dependents e001 Smith, John Agent Michael J. Susan R. e002 Andrews, David Superintendent David M. Jr. e003 Johns, Franklin Agent Andrew K. Mark W. Louisa M. ... ... ... ...
  ⇓ (Transforming)
  employee eid ename position dependent1 dependent2 dependent3 ... e001 Smith, John Agent Michael J. Susan R. e002 Andrews, David Superintendent David M. Jr. e003 Johns, Franklin Agent Andrew K. Mark W. Louisa M. ... ... ... ... ... ... ...
  ⇓ (Transforming)
  employee eid ename position e001 Smith, John Agent e002 Andrews, David Superintendent e003 Johns, Franklin Agent ... ... ...		dependent eid dname e001 Michael J. e001 Susan R. e002 David M. Jr. e003 Andrew K. e003 Mark W. e003 Louisa M. ... ...

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Slide 12.5: Tables and relations Slide 12.7: The relational rules (cont.) Home         Print version

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“Whenever you find yourself on the side of the majority,           it is time to reform (or pause and reflect).”           ― Mark Twain