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write short notes on relational modelthe relational model uses a collection of tables to show both data and the relationships between those data the
define the terms i ddl ii dmlddl data base schema is particular by a set of definitions expressed by a special language known as a data definition
explain the two types of participation constraint1 total the participation of an entity set e in a relationship set r is said to be total if each
what does the cardinality ratio specifymapping cardinalities or cardinality ratios state the number of entities to which another entity can be
define weak and strong entity setsweak entity set entity set that do not have key attribute of their own are known as weak entity setsstrong entity
define the terms i key attribute ii value set key attribute an entity type usually has an attribute whose values are exact from each individual
what is meant by the degree of relationship setthe degree of relationship type is the number of participating entity
define the terms i entity type ii entity setentity type an entity type describes a collection of entities that have the similar attributesentity set
define null valuesin some cases a certain entity may not have an applicable value for an attribute or if we do not know the value of an attribute for
what are composite attributescomposite attributes can be separated in to sub
what are stored and derived attributesstored attributes the attributes keeps in a data base are known as stored attributesderived attributes the
define single valued and multivalued attributessingle valued attributes attributes with a single value for a particular entity are known as single
define the terms i entity set ii relationship setentity set the set of all entities of the similar type is termed as an entity setrelationship set
what is relationship give examplesa relationship is an association between several entitiesexample a depositor relationship associates a customer
what are attributes give examplesan entity is shown by a set of attributes attributes are descriptive properties possessed by every member of an
what is an entity relationship modelthe entity relationship model is a set of basic objects known as entities and relationship between those objects
describe an data dictionarya data dictionary is a data structure which keeps meta data about the structure of the database ie the schema of the
list the data structures implemented by the storage managerthe storage manager executes the following data structurea data filesb data dictionaryc
what is the purpose of storage managerthe storage manager is responsible for the followinga interaction with the file managerb translation of dml
what are the components of storage managerthe storage manager components includea authorization and integrity managerb transaction managerc buffer
what is storage managera storage manager is a program module that gives the interface among the low level data keeps in a database and the
define data modela data model is a collection of conceptual tools for explaining data data relationships data semantics and consistency
what is conceptual schemathe schemas at the view level are known as subschema that describe dissimilar views of the
define the terms 1 physical schema 2 logical schemaphysical schema the physical schema explains the database design at the physical level which is
define instance and schemainstance collection of data stored in the data base at a certain moment isschema the overall design of the data base is