Fourth Normal Form
- In a many-to-many relationship, independent entities can not be stored in the same table.
Since it only applies to the many-to-many relationship, most developers can rightfully ignore this rule. But it does
come in handy in certain situations, such as this one. We’ve successfully streamlined our urls table to remove
duplicate entries and moved the relationships into their own table.
Fifth Normal Form
cases probably not required to get the most functionality out of your data structure or application. It’s tenet suggests:
- The original table must be reconstructed from the tables into which it has been broken down.
The benefit of applying this rule ensures you have not created any extraneous columns in your tables,
and that all of the table structures you have created are only as large as they need to be. It’s good practice to apply
this rule, but unless you’re dealing with a very large data schema you probably won’t need it.
database projects. And in case you’re wondering where all of this came from, the first three rules of normalization
were outlined by Dr. E.F. Codd in his 1972 paper, “Further Normalization of the Data Base Relational Model”. Other rules
have since been theorized by later Set Theory and Relational Algebra mathematicians.