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what is storage manager a storage manager is a program module that gives the interface between the low
define the terms 1 physical schema 2 logical schema physical schema the physical schema explains the database design at the physical level
define instance and schema instance collection of data kept in the data base at a particular moment is
normal 0 false false false en-in x-none x-none microsoftinternetexplorer4
timestamps for read operationsif ts t lt w-timestamp q then the transaction t is trying to read a value of data item q which has already been
timestamp ordering protocola timestamp is a tag that can be attached to any transaction or any data item which indicates a specific time on which the
explain growing phase of lockinggrowing phase in this phase the transaction can only obtain locks but cannot release any lock the transaction enters
depending upon the rules we have found we can classify the locks into two typesshared lock a transaction might be acquiring shared lock on a data
lock based protocola lock is nothing but a mechanism that tells the dbms whether a particular data item is being used by any transaction for
what is a transaction a transaction is an event which happens on the database generally a transaction reads a value from the database or writes a
multilevel index the multilevel index is a modification of the secondary level index system in this system we might be use even more number of levels
what is secondary indexwhile making the index generally the index table is kept in the primary memory ram and the main table because of its size is
primary indexin primary index there is a one-to-one relationship among the entries in the index table and the records in the major table primary
what is an indexan index is a small table having only two columns the first column has a copy of the primary or candidate key of a table and the
fifth normal form 5nfthese relations still have a difficulty while defining the 4nf we mentioned that all the attributes depend upon each other
fourth normal form 4nf when attributes in a relation have multi-valued dependency further normalization to 4nf and 5nf are needed let us first find
boyce-code normal form bcnfa relationship is said to be in bcnf if it is already in 3nf and the left hand side of each dependency is a candidate key
first normal form and second normal formfirst normal form 1nfa relation is said to be in 1nf if it having no non-atomic values and each row can give
un-normalized form unfif a table having non-atomic values at every row it is said to be in unf an atomic value is something that cannot be further
define network dbmsthe ndbms is built primarily on a one-to-many relationship but where a parent-child representation between the data items cannot
what is hierarchical dbmsin hdbms data is structured in a tree like manner there is a parent-child relationship between data items and the data model
what is relational dbmsthis is our subject of study a dbms is relational if the data is organized into relations that is tables in rdbms all data are
determine the strong and weak entitybased on the method of foreign key there might be arise a situation when we have to relate an entity having a
what is foreign keyforeign key sometimes we may have to work with an attribute that does not have a primary key of its own to recognize its rows we
describe the composite keycomposite key sometimes one key is not enough to uniquely recognize a row eg in a single class roll is enough to search a