4 Paradigm problems with database schemas.

has a relationship R (s,d,m), whose function depends on set f={s→d,d→m}. Then the relationship R satisfies
______。 [American famous search engine company face question]

A. 1NF
B. 2NF
C. 3NF
D. BCNF
Analysis: 4 paradigm Problems of database schema.
1NF: First paradigm. If each value in the domain of all properties of the relational mode R is a non-re-decomposed value,
is called R belongs to the first paradigm pattern. If a database schema is in the first paradigm, it is said that the database schema is part of the
a paradigm of the database schema.
the pattern of the first paradigm requires that the attribute value be no longer split into smaller parts, that is, attribute items cannot be attribute combinations or belong to a group
sexual composition.
2NF: Second paradigm. If the relationship pattern R is the first paradigm, and each of the non-primary properties in R has a full function dependent on
a candidate key for R, which is called R as the second normal pattern. If each relational pattern in a database schema is a second
, the database schema belongs to the second paradigm of the database schema. (Note: If A is a candidate key for Relationship mode R
Is called A is the main property of R, otherwise a is a non-primary property of R. )
3NF: The third paradigm. If the relationship pattern R is the second paradigm, and each non-principal attribute does not pass a candidate that relies on R
Key, then R is the pattern of the third paradigm. If each relational pattern in a database schema is a third paradigm, it is said
R is a 3NF database schema.
BCNF:BC paradigm. If the relationship pattern R is the first paradigm, and each property does not pass a candidate key that relies on R,
so called R is the bcnf pattern.
4NF: The fourth paradigm. Set R is a relational pattern and D is a multivalued dependent collection on R. If a non-trivial form of D
when multi-valued dependent x→→y, x must be a super-key of R, then called R is the mode of the fourth paradigm.
the title belongs to transitive dependency, so it satisfies the second normal form at most.
Answer: B

4 Paradigm problems with database schemas.