# Question on Dependency Preserving Decomposition

Question on Dependency Preserving Decomposition Question 1: R(ABCD) F = {A → B, B → C, C → D, D → A} D = {AB, BC, CD} Check whether the decomposition is preserving dependency or not ? Solution : The following dependencies can be projected into the following decomposition : R1(AB) R2(BC) R3(CD) A→B B→C…

# Questions on Lossless Join

Questions on Lossless Join To Identify whether a decomposition is lossy or lossless, it must satisfy the following conditions : R1  ∪ R2 = R R1  ∩ R2 ≠ Φ and R1  ∩ R2  → R1  or R1  ∩ R2  → R2 Question 1 : R(ABC) F = {A → B, A → C} decomposed into D = R1(AB), R2(BC) Find whether D…

# Dependency Preserving Decomposition with Example

Dependency Preserving Decomposition with Example The second property of decomposition is Dependency Preserving Decomposition. If the original table is decomposed into multiple fragments, then somehow, we suppose to get all original FDs from these fragments. In other words, every dependency in original table must be preserved or say, every dependency must be satisfied by at least…

# Classification of Dependencies in DBMS

Classification of Dependencies in DBMS – S.NO Classification of Dependencies Which Normal Form Remove these Dependencies 1 Partial Dependencies Second Normal Form (2NF) 2 Transitive Dependencies Third Normal Form (3NF) 3 Multivalued Dependencies Fourth Normal Form (4NF) 4 Join Dependencies Fifth Normal Form (5NF) 5 Inclusion Dependency (Dependencies among the Relations/Tables or Databases) Partial dependencies…

## Desirable Properties of Decomposition

 Desirable Properties of Decomposition – If we apply the normal forms or normalization or schema refinement technique – Decomposition to the universal table, then it may be splitted up into different fragments. At any stage, if we combine the fragments (denormalization), it should give the original table in terms of columns and rows and it…

## Lossy Join Decomposition

 Lossy Join Decomposition : The best refinement technique for the schema design is Decomposition. Decomposition refers to decompose or break-down of the relational-schema that has many attributes into several schemas with fewer attributes. We should take care some desirable properties while doing decomposition. If we do the careless decomposition, then it will lead to a…

## Normalisation or Schema Refinement or Database design

 Normalisation or Schema Refinement or Database design Normalisation or Schema Refinement is a technique of organizing the data in the database. It is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anomalies. The Schema Refinement refers to refine the schema by using some technique. The best…