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NORMALISATION

NORMALISATION. Normal Forms: 1NF 2NF 3NF BCNF 4NF 5NF DKNF (only theoretical). 1 NF. A relation is said to be in 1nf if it has atomic values. MODIFICATION ANOMALIES. ACTIVITY (sid,activity,fee) key:sid INSERTION ANOMALIES DELETION ANOMALIES. FUNCTIONAL DEPENDENCIES.

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NORMALISATION

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  1. NORMALISATION • Normal Forms: • 1NF • 2NF • 3NF • BCNF • 4NF • 5NF • DKNF (only theoretical)

  2. 1 NF • A relation is said to be in 1nf if it has atomic values.

  3. MODIFICATION ANOMALIES • ACTIVITY (sid,activity,fee) • key:sid • INSERTION ANOMALIES • DELETION • ANOMALIES

  4. FUNCTIONAL DEPENDENCIES • BLOCK-NAMERENT • Determinant Sid (Block,Room) ACTIVITY  Fee X  (Y,Z) XY and XZ (X,Y)Z / XZ or YZ

  5. ACTIVITIES • KEY : (SID, Activity) • FDs : Activity  Fee A Relation with a Two-Attribute key (in 1NF but not in 2NF)

  6. 2NF • 1NF+ All non-key attributes are dependeb\nt on all of the key . Decomposition ACTIVITIES[SID,ACTIVITY] Act-Fee[Activity,Fee]

  7. A RELATION WITH TRANSITIVE DEPENDENCY • Key : SID • FDs : BuildingFee SIDBuildingFee

  8. Stu - hostel key : SID Bldg-Fee Key : Building ELIMINATION OF TRANSITIVE DEPENDENCY

  9. Relation in 3NF • ADVISOR • Key :( primary ) : (SID,Major) • Key :(Candidate) : (SID,Fname) • Functional Dependencies : FnameMajor

  10. Stu -Adv ($id, Fname) Key :SID Adv-sub Key : Fname Fname Major Relations in BCNF

  11. Relation with multivalued dependencies STUDENT • KEY(sid,major,activity) • multivalued sidmajor dependencies sid activity

  12. Insertion of a single tuple

  13. Insertion of two tuples

  14. stu-major key:sid,major stu-act Key:sid,activiy Elimination of MVDS

  15. Relation in 4nf • STUDENT • KEY:sid • FDS:sidshoe-size; sidmariatal-status • MVDS: sid shoe-size/ mariatal-status • 4nf if MVDS are implied by candidate keys of R

  16. 5NF • Every JD in R is implid by candidate keys of R. SPJ:

  17. SP: join over p# PJ: join over p#

  18. SPJ

  19. join over j#,s#original SPJ

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