The collection (or set) of similar relationships.

Relationship type defines a set of associations or a relationship set among a given set of entity types.

It is the number of entity type participating.

A data base schema is specifies by a set of definitions expressed by a special language called DDL.

It specifies user views and their mappings to the conceptual schema.

This language is to specify the internal schema. This language may specify the mapping between two schemas.

The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

This language that enable user to access or manipulate data as organised by appropriate data model.

It translates DML statements in a query language into low-level instruction that the query eva luation engine can understand.

It executes low-level instruction generated by compiler.

It interprets DDL statements and record them in tables containing metadata.

The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.

It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.

The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL

The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties

A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

where [Z = (R-(X U Y)) ]

It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

The domain of attribute must include only atomic (simple, indivisible) values.

It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true

In other words, if every non prime attribute is non-transitively dependent on primary key.