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Does BCNF decomposition guarantee lossless join?
3NF ensures lossless decomposition while BCNF does not. (R1,R2) is a lossless-join decomposition of R with respect to a set of FDs F if for every instance r of R that satisfies F: πR1(r) ⋈ πR2(r) = r.
Does BCNF have lossless join?
BCNF can be used to obtain a lossless join decomp into 3NF (typically, can stop earlier) but does not ensure dependency preservation.
Is it always possible to get lossless join decomposition?
When the sub relations are joined back, the same relation is obtained that was decomposed. Every decomposition must always be lossless.
Is every BCNF decomposition lossless?
i.e., for any relation there always exist a decomposition to 3NF, which is guaranteed to satisfy both the given properties. For BCNF, the decomposition is not guaranteed to satisfy both the properties. Sometimes when lossless property is satisfied, dependency preserving is no longer possible.
What is Boyce Codd Normal Form with example?
Boyce Codd normal form (BCNF) BCNF is the advance version of 3NF. It is stricter than 3NF. A table is in BCNF if every functional dependency X → Y, X is the super key of the table. For BCNF, the table should be in 3NF, and for every FD, LHS is super key.
How to solve Boyce Codd normal form ( BCNF )?
This can be solve by Boyce-Codd Normal Form (BCNF). Boyce–Codd Normal Form (BCNF) is based on functional dependencies that take into account all candidate keys in a relation; however, BCNF also has additional constraints compared with the general definition of 3NF.
Which is a lossless decomposition of your into Boyce Codd normal form?
Which of the following is a lossless-join decomposition of R into Boyce-Codd Normal Form (BCNF)?
When do you use a lossy decomposition in BCNF?
If we go through all the FD’s and none of the rows of our table get completely filled with a then it is a lossy decomposition. Also, note if it is a lossy decomposition we can always make it lossless by adding one more relation to our set of decomposed relations consisting of all attributes of the primary key.
Is there a way to make a decomposition lossless?
Also, note if it is a lossy decomposition we can always make it lossless by adding one more relation to our set of decomposed relations consisting of all attributes of the primary key. I suggest you see this video for more examples of this method.