Normalization refers to removal of redundant information from a database Design
Following are the basic normal Forms
1st Normal Form
When each table row is free of repeated data.So a relation is in first normal form if and only if all underlying domains contain atomic values
2nd Normal Form
Applies to tables that have composite keys i.e. the primary key is made up of 2 or more columns.When a table has a composite key then every column must depend on the whole key instead of a particular column.
A relation must be in 1st NF and every nonkey attribute must be fully dependent on the primary key.
3rd Normal Form
When every column in a table depends on entire primary key and no nonkey columns depend on each other.
2nd NF + nonkey attribute is non transitively dependent on primary key
Boyce-Codd Normal Form
A table is in Boyce–Codd normal form if and only if for every one of its nontrivial dependencies X → Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
4th Normal Form
A Table is in 4NF if and only if, for every one of its non-trivial multivalued dependencies X
Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
5th Normal Form
Every join dependency in R is implied by the candidate keys of R
Following are the basic normal Forms
1st Normal Form
When each table row is free of repeated data.So a relation is in first normal form if and only if all underlying domains contain atomic values
2nd Normal Form
Applies to tables that have composite keys i.e. the primary key is made up of 2 or more columns.When a table has a composite key then every column must depend on the whole key instead of a particular column.
A relation must be in 1st NF and every nonkey attribute must be fully dependent on the primary key.
3rd Normal Form
When every column in a table depends on entire primary key and no nonkey columns depend on each other.
2nd NF + nonkey attribute is non transitively dependent on primary key
Boyce-Codd Normal Form
A table is in Boyce–Codd normal form if and only if for every one of its nontrivial dependencies X → Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
4th Normal Form
A Table is in 4NF if and only if, for every one of its non-trivial multivalued dependencies X
Y, X is a superkey—that is, X is either a candidate key or a superset thereof. 5th Normal Form
Every join dependency in R is implied by the candidate keys of R
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