Types of Schema
a) internal schema.
b) Conceptual schema.
c) External schemas or user views.
Data Independency
Data independency is defined as the capacity to change the conceptual schema without having to change the schema at the next higher level. We can define two types of data independence:
a) Logical data independence, LPD
Data independency is defined as the capacity to change the conceptual schema without having to change the schema at the next higher level. We can define two types of data independence:
a) Logical data independence, LPD
b) Physical data independence, PDI
LDI is the capacity to change the conceptual schema without having to change external schemas or application programs.
LDI is the capacity to change the conceptual schema without having to change external schemas or application programs.
PDI is the capacity to change the internal schema without having
to change conceptual (or external) schemas.
DBMS Languages
a) DDL (Data definition language)
b) SDL (Storage definition language)
c) VDL (View definition language)
d) DML (Data manipulation language)
Types of DBMS
a) RDBMS (Relational)
b) ORDBMS (Object Relational)
c) DDBMS (Distributed)
d) FDBMS (Federated)
e) HDDBMS (Homogeneous)
f) HDBMS (Hierarchical)
g) NDBMS (Networked)
a) RDBMS (Relational)
b) ORDBMS (Object Relational)
c) DDBMS (Distributed)
d) FDBMS (Federated)
e) HDDBMS (Homogeneous)
f) HDBMS (Hierarchical)
g) NDBMS (Networked)
Entity
An entity is a thing in the real world with an independent existence.
An entity is a thing in the real world with an independent existence.
Attributes
These are the particular properties that describe an entity.
These are the particular properties that describe an entity.
Types of Attributes
a) Composite Vs simple attributes.
b) Single valued Vs multi-valued attributes.
c) Stored Vs derived attribute.
d) Null valued attributes.
e)Complex attributes.
a) Composite Vs simple attributes.
b) Single valued Vs multi-valued attributes.
c) Stored Vs derived attribute.
d) Null valued attributes.
e)Complex attributes.
f) What is difference between entity set and entity type?
Domain Value or Value Set of an Attribute
It is the set of values that may be assigned to that attribute for each individual entities .
It is the set of values that may be assigned to that attribute for each individual entities .
Degree of a Relationship
The no of entities participating in that relation .
The no of entities participating in that relation .
Recursive Relationship
It is the relationship where both the participating entities belong to same entity type .
It is the relationship where both the participating entities belong to same entity type .
Relationship Constraints
a) Cardinality Ratio. b) Participation Constraints.
a) Cardinality Ratio. b) Participation Constraints.
Cardinality Ratio
The cardinality ratio for a binary relationship specifies the number of relationship instances that an entity can participate in.
The cardinality ratio for a binary relationship specifies the number of relationship instances that an entity can participate in.
Participation Constraint
The participation constraint specifies whether the existence of an entity depends on its being related to another entity via the relationship type. This is of two types:
a) Total Participation.
b) Partial Participation.
The participation constraint specifies whether the existence of an entity depends on its being related to another entity via the relationship type. This is of two types:
a) Total Participation.
b) Partial Participation.
Weak Entity Types
The entity types that do not have key attributes of their own are called weak entity types.
Rests are called strong entity types .The entity that gives identity to a weak entity is called owner entity. And the relationship is called identifying relationship. A weak entity type always has a total participation constraint with respect to its identifying relationship.
The entity types that do not have key attributes of their own are called weak entity types.
Rests are called strong entity types .The entity that gives identity to a weak entity is called owner entity. And the relationship is called identifying relationship. A weak entity type always has a total participation constraint with respect to its identifying relationship.
ER Diagram/ EER Diagram
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.
Specialization
It is the process of defining a set of subclasses of an entity type where each subclass contain all the attributes and relationships of the parent entity and may have additional attributes and relationships which are specific to itself.
It is the process of defining a set of subclasses of an entity type where each subclass contain all the attributes and relationships of the parent entity and may have additional attributes and relationships which are specific to itself.
Generalization
It is the process of finding common attributes and relations of a number of entities and defining a common super class for them.
It is the process of finding common attributes and relations of a number of entities and defining a common super class for them.
Generalization and Specialization
a) Disjoint ness constraints.
b) Completeness constraints.
a) Disjoint ness constraints.
b) Completeness constraints.
c) Total Specialization constraints. Disjointness Constraint specifies that the subclasses of the specialization must be
disjoint .i.e. an entity can be a member of at most one of the subclasses of
the specialization. The reverse of it is overlapping. Completeness Constraint is a participation constraint which may be
i) Total
i) Total
ii) Partial Total specialization
Constraint tells that each entity in the super class
must be a member of some subclass in the specialization. And partial
specialization constraint allows an entity not to belong to any of the
subclasses .Thus we do have the following 4 types of constraints on
specialization:
i) Disjoint, total
i) Disjoint, total
ii)Disjoint, partial
iii)Overlapping, total
iv)Overlapping, partial
iii)Overlapping, total
iv)Overlapping, partial
Ternary Relationship
A relationship with a degree 3 is called a ternary relationship.
A relationship with a degree 3 is called a ternary relationship.
Aggregation and Association
Aggregation is an abstraction concept for building composite objects from their component objects. The abstraction of association is used to associate objects from several independent classes.
Aggregation is an abstraction concept for building composite objects from their component objects. The abstraction of association is used to associate objects from several independent classes.
RAID Technology
Redundant array of inexpensive (or independent) disks. The main goal of raid technology is to even out the widely different rates of performance improvement of disks against those in memory and microprocessor. Raid technology employs the technique of data striping to achieve higher transfer rates.
Hashing Technique
This is a primary file organization technique that provides very fast access to records on certain search conditions. The search condition must be an equality condition on a single field, called hash field of the file.
a) Internal hashing
b) External hashing
c) Extendible hashing
d) Linear hashing
e) Partitioned hashing
Types of Relational Constraints
a) Domain Constraints
b) Key Constraints
a) Domain Constraints
b) Key Constraints
c) Entity Integrity Constraints
d) Referential Integrity Constraints Domain Constraints specify that the value of each attribute must be an atomic value from the domain of the attributes. Key Constraints tell that no two tuples can have the same combination of values for all their attributes. Entity Integrity constraint states that no primary key value can be null. Referential Integrity constraints states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation it is specified between two relations and is used to maintain the consistency among tuples of the two relations.
d) Referential Integrity Constraints Domain Constraints specify that the value of each attribute must be an atomic value from the domain of the attributes. Key Constraints tell that no two tuples can have the same combination of values for all their attributes. Entity Integrity constraint states that no primary key value can be null. Referential Integrity constraints states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation it is specified between two relations and is used to maintain the consistency among tuples of the two relations.
Super Key, Key, Candidate Key, Primary Key
A Super Key specifies a uniqueness constrain that no two distinct tuples in a state
can have the same value for the super key. Every relation has at least one default super key. A Key is a minimal super key or the subset of the super key which is obtained after
removing redundancy. A relation schema may have more than one key .In this case
each key is called a candidate key. One of the candidate key with minimum number
of attributes is chosen as primary key.
A Super Key specifies a uniqueness constrain that no two distinct tuples in a state
can have the same value for the super key. Every relation has at least one default super key. A Key is a minimal super key or the subset of the super key which is obtained after
removing redundancy. A relation schema may have more than one key .In this case
each key is called a candidate key. One of the candidate key with minimum number
of attributes is chosen as primary key.
Foreign Key
A key of a relation schema is called as a foreign key if it is the primary key of
some other relation to which it is related to.
A key of a relation schema is called as a foreign key if it is the primary key of
some other relation to which it is related to.
Transaction
A transaction is a logical unit of database processing that includes one or more database access operations. If a Transaction is not complete it rolled back or cancelled.
A transaction is a logical unit of database processing that includes one or more database access operations. If a Transaction is not complete it rolled back or cancelled.
Properties of Transaction
a) Atomicity
b) Consistency preservation
c) Isolation
d) Durability (permanence)
a) Atomicity
b) Consistency preservation
c) Isolation
d) Durability (permanence)
Basic database Operations
a) Write_item(x) – Insert Command
b) Read_item(x) – Select Command
a) Write_item(x) – Insert Command
b) Read_item(x) – Select Command
Disadvantages of not controlling concurrency
a) Lost update problem
b)Temporary update(Dirty read) problem
c) Incorrect summary problem
a) Lost update problem
b)Temporary update(Dirty read) problem
c) Incorrect summary problem
Serial, Non serial Sechedule
A schedule S is serial if, for every transaction T participating in the schedule, all the operations of T is executed consecutively in the schedule, otherwise, the schedule is called non-serial schedule.
A schedule S is serial if, for every transaction T participating in the schedule, all the operations of T is executed consecutively in the schedule, otherwise, the schedule is called non-serial schedule.
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