What are Armstrong rules? How do we say that they are complete and/or sound?
Submitted by: AdministratorThe well-known inference rules for FDs
? Reflexive rule :
If Y is subset or equal to X then X Y.
► Augmentation rule:
If X Y then XZ YZ.
► Transitive rule:
If {X Y, Y Z} then X Z.
► Decomposition rule :
If X YZ then X Y.
► Union or Additive rule:
If {X Y, X Z} then X YZ.
► Pseudo Transitive rule :
If {X Y, WY Z} then WX Z.
Of these the first three are known as Amstrong Rules. They are sound because it is enough if a set of FDs satisfy these three. They are called complete because using these three rules we can generate the rest all inference rules.
Submitted by: Administrator
? Reflexive rule :
If Y is subset or equal to X then X Y.
► Augmentation rule:
If X Y then XZ YZ.
► Transitive rule:
If {X Y, Y Z} then X Z.
► Decomposition rule :
If X YZ then X Y.
► Union or Additive rule:
If {X Y, X Z} then X YZ.
► Pseudo Transitive rule :
If {X Y, WY Z} then WX Z.
Of these the first three are known as Amstrong Rules. They are sound because it is enough if a set of FDs satisfy these three. They are called complete because using these three rules we can generate the rest all inference rules.
Submitted by: Administrator
Read Online RDBMS Job Interview Questions And Answers
Top RDBMS Questions
☺ | What is VDL (View Definition Language)? |
☺ | Difference between controlled and uncontrolled redundancy? |
☺ | What is RDBMS KERNEL? |
☺ | What is SDL (Storage Definition Language)? |
☺ | What is 5NF? |
Top Databases Programming Categories
☺ | RDBMS Interview Questions. |
☺ | SQL Interview Questions. |
☺ | SSRS Interview Questions. |
☺ | Sybase Interview Questions. |
☺ | Database Administrator (DBA) Interview Questions. |