Please enable JavaScript.
Coggle requires JavaScript to display documents.
NORMALIZATION, FUNCTIONAL DEPENDENCIES, CLOSURE METHOD, CANONICAL COVER,…
NORMALIZATION
-
-
COLUMN-LEVEL DUPLICACY
-
FIRST NORMAL FORM
-
SECOND NORMAL FORM
- The table should be in 1NF
- There should be no partial dependency.
- no non-prime attribute is dependent on any proper subset of any candidate key of the table.
-
LHS should be a part of candidate key and RHS should be a non-prime attribute then there is partial dependancy
THIRD NORMAL FORM
- The table should be in 2NF
- There should be no transitive dependency for non-prime attributes.
What we want is that the non-prime attributes should be fully dependent on candidate keys, and should be derived by them only
-
-
-
CLOSURE METHOD
-
First check for the missing attribute that is not getting determined
- Check the missing attribute by getting all the attributes on the right hand side
---> Now this attribute should be present in your candidate key for sure.
Now once you get a candidate key, check if the attributes in the candidate key are getting determined by any attribute, if so replace the attribute and you will get another candidate key.
CANONICAL COVER
- Make the right hand side of each FD a single attribute
- Drop the redundant dependencies
- If possible make the LHS of FD's single value attribute.
A canonical cover of a set of functional dependencies F is a simplified set of functional dependencies that has the same closure as the original set F.
FINDING CANDIDATE KEYS
- If some attribute is not being determined (not present in RHS)then it should be present in the candidate key
-
- All the other forms ensures DEPENDENCY PRESERVING DECOMPOSITION except BCNF because it may or may not preserve dependency during decompositon
- All the normal forms ensures LOSSLESS DECOMPOSITION :check:
-
LOSSLESS JOIN
Union of Attributes of R1 and R2 must be equal to attribute of R. Each attribute of R must be either in R1 or in R2.
-
-
-
-
-