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unit 1 Flashcards

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1
Q

What is data

A

Raw input. Known facts, can be recorder, have implicit meaning.

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2
Q

What is information?

A

Processed data.

When data is processed, organized, structured and presented to make it useful.

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3
Q

relationship btwn data and info

A

data independent whereas info is dependent on data

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4
Q

What is Database

A

DBMS is storing or collection of related data. Represents aspects of mini world or UOD.
Has implicit meaning.
Logically coherent.
Can be of any size.

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5
Q

DBMS

A

General purpose software system that facilitates the process of defining, constructing, manipulating and sharing databases among various users.

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6
Q

Why use Databases

A

Store it, understand it, keep it secure, find it and use it.

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7
Q

Database environment components

A

Database system, database software, users and programmers send in queries that is in db system, software to process queries, software to access the data, present in dbms software, metadata (stored database definition), and stored data.

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8
Q

What does metadata do?

A

Data which provides information about the other data.

It helps us to structure the table.

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9
Q

What are the different characteristics of the database approach?

A
  • self describing nature of the database
  • program database independence
  • multiple views support
  • sharing of data nd multiple user transaction processing
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10
Q

State 5 advantages of using the database.

A

Controlling the data redundancy.
Multiple users can access the data at the same time.
Project oriented.
Prevents unauthorized access to the data.
Well protected data.
Boundary between the program and the actual database.
Backup and recovery.
Flexibility to change the data structures.
Availability of current information.

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11
Q

What is a data model?

A

It refers to the collection of objects that are used to describe the structure of the database. Necessary means to achieve data abstraction.
2 distinct but closely related concepts -> abstract formalization of objs and rships.

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12
Q

What are constructs?

A

Used to define the structure of the database.

elements and their data types.

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13
Q

Constraints function?

A

To put some restriction on valid data.

They must be defined at all times.

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14
Q

What are the common operations of the database and are they included in the concepts?

A

Select, update, insert, delete

yes

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15
Q

What are the different categories of data models?

A

High level / conceptual - close to the way users perceive the data
Low level / physical model - The way data is arranged in the computer storage. Understood by comp analysts and not end users
Representational model - Data arranged in a manner that end users understand easily but not too far removed from the way data is stored in the comp storage
Self learning model - data + data description or values`

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16
Q

What is a database schema?

A

A Database schema is the description of the database.

Specified during the database design with the help of a schema diagram.

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17
Q

Does the schema change frequently?

A

NO

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18
Q

What is schema evolution?

A

It is changing the schema.

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19
Q

What is database state?

A

The actual data can change frequently in the database, and hence the data in the database at any given point of time is called as the database state or the snapshot.

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20
Q

What does the CRUD operations do for the database? What does initial state ad valid state mean?

A

It changes the state of instances,
Initial state - State of the database when it is initially loaded into the system.
Valid state - State of the database that satisfies the structure and constraints of the database.

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21
Q

Describe the three schema architecture.

A

Goal is to separate the user interface or applns from the actual physical database.

i) Internal database - provides the physical structure of the database.
ii) conceptual database - provides the structure of the whole database for the community of the users.
iii) external database - only parts of the database the user is interested in, the other parts are hidden.

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22
Q

What is data independence?

A

It is the capacity to change one level of schema without actually making changes in the higher level of schema

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23
Q

What are the different types of data independence?

Explain.

A

i) Logical data independence: making chnages in the conceptual schema without making changes on the external schema or the application programs
ii) physical data schema: making changes in the internal schema without changing the conceptual schema

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24
Q

What is DDL?

A

DATA DEFINITION LANGUAGE is used by the DBA in order to describe both the internal and the conceptual schemas for the database and any mappings between the two.
Wehn there is a clear boundary between the 2, DDL defines only the conceptual schema, SDL is used to define the internal schema.

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25
When is SDL used?
STORAGE DEFINITION LANGUAGE: is used to define internal schema when there is a clear boundary between the two.
26
What does DDL compiler do?
Processing the statements to identify descriptions of the schema constructs and to store schema description in the DBMS catalog
27
What is DML? What are the different kinds of dml?
DML stands for data manipulation language. This particular language is used for inserting, retrieving, deleting or modifying the data. i) high level DML or non procedural DML : Set at a time. As multiple data can be retrieved or specified in a single DML statement. This can be easily displayed on a terminal as such. ii) low level DML or procedural DML: Record at a time. Should be embedded into a programming language. Individual records can be accessed one at a time.
28
Specify some different kinds of DATABASE interfaces.
``` Menu based interface form based interface natural language processing speech input output interfaces for parametric users and DBA ```
29
Specify some database programming language interfaces
Embedded approach - sql embedded in c or c++ procedure call approach - jdbc for java, odbc for other db programming language approach - labgauges based on SQL like oracle scripting language approach - php and python
30
What are dbms component modules?
DDL compiler, catalog, query compiler, query optimizer, precompile, and runtime database processor.
31
CLIENT SERVER ARCH
Client server arch assumes and underlying framework which consists of many workstation sor pcs and lesser number of servers that are connected via wireless network or LAN. Client - user machine providing interface capabilities and local processing. Server - both hardware and software that can provide services to clients
32
TWO TIER CLIENT SERVER ARCH
2 tier architecture, software components are divided into client and server. DBMS server runs on server clients - user machine and programs. application on client establishes connection with the server. ADV - simplicity compatibility
33
THREEE TIER
three tier consists of client server and and intermediate layer between the two which is called as the "application server" or the "web server". intermediate layer accepts req from client and processes it and sends only the queries to the server.
34
what does the database design process consist of?
Application design database design main concentration on the conceptual design
35
What is an ER Model?
Entity Relationship Diagram is a graphical representation of the schema of a database application.
36
What are entities and attributes?
Entity: basic concept represented in an ER diagram. They specify things or objects in the mini world. Attributes: They are the properties which are used to describe the entities.
37
What all does an attribute have associated with it?
Every entity has a value associated with its attributes, and every attribute has a data type associated with it.
38
What are the different types of attributes? Explain
i) simple - only one atomic value for an attribute ii) composite - one attribute may be composed of multiple components ii) multivalued - one entity may have multiple values for that attribute -> there can be multiple vals of composite attributes. i.e they are nested arbitarily iv and v) derived and stored attribute - if 2 attributes are related then one of them can be derived from the other, the one that can be derived is called as derived attribute and the other one is called as the stored attribute.
39
What do you mean by entity types?
Groups of entities that are similar. Set of entities that are having the same attributes.
40
What do you mean by a key attribute?
An attribute of an entity type for which each entity must have a unique value associated with it. It can be composite, and one entity may have multiple keys associated with it.
41
What do you mean by entity set?
Every database consists of collection of entities stored in its database which is called as entity set or collection. It represents the current state or collection.
42
What do you mean by value sets?
Set of values for a particular attribute. Similar to data types. Every simple attr is associated with a value set.
43
Mathematical relationship btwn value, attr and entity type
A: E -> P(V) (all possible subsets)
44
What do you mean by relationships?
Relationship relates two or more distinct entities with a specific meaning.
45
What do you mean by relationship types? Relationship set?
Relationships of the same types are put into the same relationship type. Relationship set R is a set of relationship instances Ri.
46
What do you mean by relationship degree?
The degree of a relationship type is the number of participating entity types.
47
different types of relationship degree?
binary - degree 2 | ternary - degree 3
48
Relationship role name?
Specifies the role that an entity of entity type plays in the relationship instance. This helps explaining the relationship.
49
What do you mean by recursive relationship or self referencing relationships?
In some cases, same entity type participates more than once in the same relationship type in different roles.
50
What do you mean by constraints on a relationship? What are different constraints available?
Relationship types have certain constraints that limit the possible combinations of entities that may participate in corresponding relationship sets. Cardinality ratio and participation constraint - together they make up the structural constraint
51
What do you mean by cardinality ratio? explain
For any binary relationship, cardinality ratio specifies the maximum number of relationship instances that an entity can participate in. 1:N, N:1, M:N, 1:1
52
What do you mean by participation constraint and existence dependencies?
It is the minimum number of relationships that each entity can participate in. minimum cardinality ratio. total participation -> existence dependency "total and partial"
53
Attributes on relationship types
Attributes can be applied to relatioship types, in a similar way of entity types. Attributes on 1:1 1:N types can be migrated to one of the participating entity types. 1: 1 - either of the entity types 1: N - migrated to only the N side of the entity type.
54
How are the following represented in an ER Diagram? i) Relationships ii) attributes iii) total and partial participation iv) entity
rhombus oval double line and single line rectangle
55
What do you mean by weak entity type?
A weak entity type is th one that has no key attributes of its own. The entities that belong to these entity types are identified by being related to specific entities from another entity type in combination with one of their attr vals Other entity -> owner entity or identifying entity relationship relating them -> identifying relationship always a total participation from weak entity to identifying relationship.
56
CHARS OF WEAK ENTITY TYPE?
Weak entity type normally has a partial key that can uniquely identify weak entities belonging to the same owner entity. They can be represented as complex or composite. any number of levels of weak entity can be found owner entity can itself be a weak entity can have multiple owner entities relationship degree > 2 for the identifying relationship
57
How do you refine a ER diagram?
By changing the attributes representing the relationship into relationship types. Figure out cardinality ratios and participation constraints Always important to have the least possible redundancy -> entity tyoes and relationships are in capital letters -> Attribute names have first letter capital -> role names are in lower case * concept should be modelled as an attribute and then refined into relationship. Attribute can be a reference to another entity type. * attribute existing in several entity types must be made into a independent entity type.
58
Ternary relationship? How can it be more refined?
Relationship type where the participating entities are 3. | By doing 3 binary relationship.
59
What is a condition in 3 binary relationships.
if 3 binary relationship exists, it doesn't really mean that a ternary relationship exists between the three
60
How to chose between binary relationships and ternary or higher relationships
common soln - ternary rship plus one or more binary relationships. Ternary relationship can also be represented as a normalentity typeby introducing a artificial or a surrogate key.
61
What are the 2 notations used to represent the higher degree rships?
i) based on cardinality ratio - specified on each arc | ii) min max notation participation
62
Intension and extension specify.
Intension - data schema | extension - data state

DBMS (2 decks)

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