SEPTEMBER / OCTOBER-2009[12BCA38,12BCA37,12BCA40]€¦ · Web viewA transaction is a collection...
Transcript of SEPTEMBER / OCTOBER-2009[12BCA38,12BCA37,12BCA40]€¦ · Web viewA transaction is a collection...
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Sr.no Que-Ans Marks
Q-1 Answer the following question. 12.
1 What is data manager? List the responsibilities of the database
manager.
Ans: Data manager is the central software components of the DBMS. Responsibilities of data manager are Responsible for interfacing with file system. Enforcing constrain to maintain the consistency and integrity of
data. Maintaining security Convert operations in users query.
2 Define the team :
A.Database schema :
B.Database:
Ans: A. Database schema :
In a relational database the schema define the table the
field in each table and the relationship between fields and
table.
Schema has a two types
1. Physical schema.
2. Logical schema.
B. Database:
A systematic type of argument of related information is
called a database.
3. Differentiate between physical and logical data independence.
Ans: Physical Independence: It indicates that the physical storage structure of storage or devices used for storing could be changed without necessity a change in conceptual view or any of the external views. Logical independence: It indicates that the conceptual schema can
be changed without affecting the existing external schemas.4. Explain association with example.
Ans: A relationship is an association among several entities. For Eg.customer and loan are two entities we can define a relation that
associated customer Harish with loan L-1.5. Explain query processor.
Ans: Function of query processor is to break down DML statement into instruction the storage manager understands.
Component of processor are DDL interpreter query that the which interprets DDL statement.
DML compiler which translate DML statement in a query language into evaluation plan.
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Query evaluation engine which executes low level instruction generated by DML compiler.
6. State the difference between functional and multivalued
dependencies.
Ans: Functional dependencies :Given two set of attributes X&Y.Y is said to be functionally dependant on X it a given for each attributes in X uniquely determines the values of the attributes in Y.X is called the determinant of the functional
Dependency (fd) and fd is denotes by X>Y. Multivalued dependencies. : Given a relation schema R, let X&Y be subset of attributes of R and Y need not be distinct. Then multivalued dependencies x>y hold in a relation R define R if
given two tuples t1 and t2 in R with t1(X)=t2(X) R contain two tuples t3 and t4 with the following characteristics:
T1, T2, T3 and T4 the same values X. T1(X)=t2(X)=t3(X)=t4(X) The Y values of t1 and t3 are the same The Y values of t2 and t4 the
same T1(Y)=t2(Y)=t3(Y)=t4(Y)
Q2. Answer in brief.
a. Write a note on database system user.
Ans: Application programmers – interact with system through DML callsSophisticated users – form requests in a database query language Specialized users – write specialized database applications that do not fit into the traditional data processing framework.
Naïve users – invoke one of the permanent application programs that have been written previously E.g. people accessing database over the web, bank tellers, clerical
staff Users are differentiated by the way they expect to interact with the
system A transaction is a collection of operations that performs a single
logical function in a database application. Transaction-management component ensures that the database
remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.
Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.
08.
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(or)
a. Discuss type of record-base logical model. Differentiate them with each other.
Ans: 1. Record-based logical models: Also describe data at the conceptual and view levels. Unlike object-oriented models, are used to Specify overall logical
structure of the database, and provide a higher-level description of the implementation.
Named so because the database is structured in xed-format records of several types.
Each record type de nes a xed number of elds, or attributes. Each end is usually of a xed length (this simpli es the
implementation). Record-based models do not include a mechanism for direct
representation of code in the database. Separate languages associated with the model are used to express
database queries and updates. The three most widely-accepted models are the relational, network,
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and hierarchical.
Name street city number
Lowery Maple Queens 900
Shiver North Bronx 556
Shiver North Bronx 647
Hodges Sidehill Brooklyn 801
Hodges Sidehill Brooklyn 647
This course will concentrate on the relational model. The network and hierarchical models are covered in appendices in the
text.
The Relational Model: Data and relationships are represented by a collection of tables. Each table has a number of columns with unique names, e.g. customer, account Figure 1.3 shows a sample relational database.Figure 1.3: A sample relational database.
Figure 1.4: A sample network database
The Network Model: Data are represented by collections of records. Relationships among data are represented by links. Organization is that of an arbitrary graph. Figure 1.4 shows a sample network database that is the equivalent of
the relational database of Figure 1.3.The Hierarchical Model Similar to the network model. Organization of the records is as a collection of trees, rather than
arbitrary graphs. Figure 1.5 shows a sample hierarchical database that is the equivalent
of the relational database of Figure 1.3.Figure 1.5: A sample hierarchical database
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The relational model does not use pointers or links, but relates records by the values they contain. This allows a formal mathematical foundation to be defined.
b. Define relationship. Explain types of relationship with
example.
Ans: A relationship is an association among several entities.For example a depositor relation ship assosiated customer with each account that she/he has.
The number of entities set that partcipate in a relationship set is also the relationship set is of degree 3.
Various types of relationship are Binary relationship ternary relationship
Binary relationship: The relationship set borrow and loan branch provide an example of a
binary relationship set that is one that involes two entities set.
As example considers the entity set employee, branch and job.
Examples of job could include manager teller auditor and so on job
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entities may have the attributes title and level.
The relationship set works on among employee branch and job is an example of a ternary relationship.
(or)
b. Compare BCNF and 3RD NF.
Ans: BCNF 3RD NF1 In BCNF for every x>y,
Y is subset of X X is super key.
In 3NF for every X>Y, Y is subset of X. X is not super key. Y is not subset of key.
2 BCNF don’t have any redundancy.
3NF has some redundancy
3 BCNF is not dependency preserving.
3NF is dependency preserving
4 The relation in #NF is now decomposed to bring it to BCNF FD of original tables are FD:FD1:stu#,sub>teacherFD:FD2: stu#,sub>scoreFD:FD3: stu#,sub>subExample:Teac Sub
Teacher SubjectRaturi Chem.Siya EnglishJiya HistoryRitika CS
FD 1: teacher >subjectStu# Sub1H123 Chem.1H124 English1H234 History1H254 CS1H235 Chem.
FD11:stu#,sub>scoreAs per FDs inferd from teach_sub&stu#_score tableside are fd1:teacher>subjectFd2:stu#,sub,sub>scoreOriginal tables have 2 FDs and also not same as original table.Thus in BCNF dependency not preserved.
Example:Stud# Sub teache
rScore
1H123
chem Raturi 4
1H124
English
Siya 4
1H234
History
Jiya 3
1H254
CS Ritika 3
1H235
chem Roma 2
FD:FD1:stu#,sub>teacherFD:FD2: stu#,sub>scoreFD:FD3: teacher>subKey:stu#sub
In FD1,fd2,fd3 there is no partial dependency so relation is in 2NF.
In fd1 stu#,sub is key in fd2 Stu#, sub is key and in fd3 sub at dependant side is prime attribute and as per 3NF either determinant should be key or dependant is prime attribute so this relation is in 3NF.
3.but still having data redundancy
05.
Q-3 Write a short note on any three with an example. 21.
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1. Explain Generalization and Specialization.
Ans: Consider extending the entity set account by classifying accounts as being either saving-account or chequing-account.
Figure : Generalization
Each of these is described by the attributes of account plus additional attributes. (savings has interest-rate and chequing has overdraft-amount.)
We can express the similarities between the entity sets by generalization.
This is the process of forming containment relationships between a higher-level entity set and one or more lower-level entity sets.
In E-R diagrams, generalization is shown by a triangle, as shown in Figure. Generalization hides dierences and emphasizes similarities. Distinction made through attribute inheritance. Attributes of higher-level entity are inherited by lower-level
entities. Two methods for conversion to a table form:
_ Create a table for the high-level entity, plus tables for the lower-level entities containing also their specific attributes._ Create only tables for the lower-level entities.
Specialization Top-down design process; we designate sub groupings within an
entity set that are distinctive from other entities in the set. These sub groupings become lower-level entity sets that have
attributes or participate in relationships that do not apply to the higher-level entity set.
Depicted by a triangle component libelled ISA (E.g. customer “is a” person).
Attribute inheritance A lower-level entity set inherits all the attributes and relationship participation of the higher-level entity set to which it is linked.
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2. Date manipulation statement in sql.Ans: Data Manipulation(DML) :
retrieval of information from the database insertion of new information into the database deletion of information in the database modication of information in the database A DML is a language which enables users to access and
manipulate data. The goal is to provide ecient human interaction with the system. There are two types of DML
Procedural: The user species what data is needed and how to get it Nonprocedural: The user only species what data is needed
Easier for user May not generate code as ecient as that produced by
procedural languages A query language is a portion of a DML involving
information retrieval only. The terms DML and query language are often used synonymously.
Data Manipulation Language (DML): DML statements are used for managing data within schema objects. Some example:
Command DescriptionSELECT: Retrieve data from the a databaseINSERT: Insert data into a tableUPDATE: Update existing data within a tableDELETE: Deletes all records from a table, the space
for the records remainMERGE: UPSERTE operation (insert or update)CALL: Call a PL/SQL or java subprogramEXPLAI PLAN:
Explain access path or data
LOCK TABLE: Control concurrency
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3. Integrity constraint.
Ans: Integrity constrain are used to ensure accuracy and consistency
of data in a relational database.
Data integrity is handled in a relational database through the
concept or referential integrity.
There are many type of integrity constrain.
Entity integrity.
Referential integrity.
Domain integrity.
Entity integrity :-
Entity integrity is an integrity rule which states that every
table must have a primary key and that the column or chosen to be
the primary key should be unique and not null.
If each value of a primary key must be unique no duplicate row
can logically appear in a table.
The not NULL characteristic of a primary key ensures that a
value can be use to identify all rows in a table.
Within relational database using SQL, entity integrity is
enforced by adding a primary key cause to a schema definition.
Referential integrity:
There are cases where we wish to ensure that a value that
appears in one relation for a given set of attribute also appears for
a certain set of attributes in another relation this is called
referential integrity.
Database modification can cause violation of referential
integrity.
When a referential integrity constrain is violated the normal
procedure is to reject the action that caused violation.
Example:
Emp(eid,ename,add,contect_no,);
Dept(dptid,dptname);
Emp_dept(empid,dptid);
In table it can be enforced using following example.
CREATE TABLE EMP
(
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EID NUMBER PRIMARY KEY,
ENAME TEXT,
ADD TEXT,
CONTACTECT_NO NUMBER
);
Domain integrity:
A domain defines the possible values of an attribute.
Domain integrity rules govern these values.
In a database system the domain integrity is define by,
The data type and the length
The NULL value acceptance
The allows able values, through techniques like constrain
or rules
The default value.
4. Mapping cardinalities.Ans:
Express the number of entities to which another entity can be associated via a relationship set.
Most useful in describing binary relationship sets.
For a binary relationship set the mapping cardinality must be one of the following types:
1.One to one2.One to many3.Many to one4.Many to many
Explain in brief
1. One to One
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One to one One to many
Note: Some elements in A and B may not be mapped to any
elements in the other set
Many to one Many to many
Note: Some elements in A and B may not be mapped to any
elements in the other set
Mapping Cardinalities affect ER Design
Can make access-date an attribute of account, instead of a relationship attribute, if each account can have only one customer
I.e., the relationship from account to customer is many to one, or equivalently, customer to account is one to many .
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E-R Diagrams
Rectangles represent entity sets.Diamonds represent relationship sets.Lines link attributes to entity sets and entity sets to relationship sets.Ellipses represent attributesDouble ellipses represent multivalued attributes.
Dashed ellipses denote derived attributes.Underline indicates primary key attributes (will study later)
E-R Diagram With Composite, Multivalued, and Derived Attributes
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Relationship Sets with Attributes
Roles:
Entity sets of a relationship need not be distinct
The labels “manager” and “worker” are called roles; they specify how employee entities interact via the works-for relationship set.
Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles.
Role labels are optional, and are used to clarify semantics of the relationship
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Cardinality Constraints
We express cardinality constraints by drawing either a directed line (®), signifying “one,” or an undirected line (—), signifying “many,” between the relationship set and the entity set.
E.g.: One-to-one relationship:
A customer is associated with at most one loan via the relationship borrower
A loan is associated with at most one customer via borrower
One-To-Many Relationship
In the one-to-many relationship a loan is associated with at most one customer via borrower, a customer is associated with several (including 0) loans via borrower
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Many-To-One Relationships
In a many-to-one relationship a loan is associated with several (including 0) customers via borrower, a customer is associated with at most one loan via borrower
Many-To-Many Relationship
A customer is associated with several (possibly 0) loans via borrower
A loan is associated with several (possibly 0) customers via borrower
Q-4 Answer the following : 12.
A. Describe the need of normalization and steps to achieve BCNF.
Ans: Definition :
Normalization is the process to filtering database which is to
reduce a normalization and redundancies data.
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Normalization is the process of efficiently organising data in
data base.
Goal :
Eliminate redundant data.
Ensuring redundant data is logically staror.
Purpose:
Normalization is the technique for producing a set of relation
with describes properties, given the data requirement of an
enterprise.
The process of normalization is a formal method that identifies
relation base on their primary & candidate key and the
functional dependencies among their attribute.
Need of normalization: Database normalization is the process of organizing the fields
and tables of a relational database to minimize redundancy and dependency.
Normalization usually involves dividing large tables into smaller (and less redundant) tables and defining relationships between them.
A database table looks like a spreadsheet. One item of data, such as a first name, a last name, a phone number,
or a street address, appears in each box, or cell, at each intersection of a row and column.
When you normalize a database you have four goals: Arranging data into logical groupings such that each group
describes a small part of the whole Minimizing the amount of duplicate data stored in a database; Organizing the data such that, when you modify it, you make
the change in only one place Building a database in which you can access and manipulate
the data quickly and efficiently without compromising the integrity of the data in storage.
Data normalization helps you design new databases to meet these goals or to test databases to see whether they meet the goals.
Sometimes database designers refer to these goals in terms such as data integrity, referential integrity, or keyed data access.
Normalization is a process followed for eliminating redundant data and establishes a meaningful relationship among tables based on rules and regulations in order to maintain integrity of data.
Normalization is done for maintaining storage space and also for performance tuning.
1st Normal form :
Rule 1: Eliminate Repeating Groups. Make a separate table for each set of related attributes, and give each table a primary key.
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First NF is a relation in which the intersection of each row and
column contain one value.
There are two approaches to removing repeating group for
unnormalization table.
Remove the repeating group by entering appropriate data in
the empty column of row contains the repeating data.
Remove repeating group by placing the repeating data
along with a copy of the original key attribute in a
shaparate relation a primary key is identify for the new
relation.
2nd Normal Form :
Rule 2: Eliminate Redundant Data, if an attribute depends on only part of a multi-valued key, remove it to a separate table.
Second NF is a relation that is in first normal form and every
non-primary key attribute is fully functionally dependent on
the primary key.
Second NF is removing partial dependencies if a partial
dependency exists; we remove the function dependency
attributes form the form the relation by placing them in a new
relation among with a copy of their determinant.
3rd normal form :Rule 3: Eliminate columns not dependent on key. If attributes do not contribute to a description of the key, remove them to a separate table.
A relation that is in first n & second normal form and in which
no none primary key attribute is transitively dependent on the
primary key.
Third nf is remove transitive dependency by placing the
attribute in a new relation among with a copy of the
determinant.
BCNF :Rule 4: Isolate independent multiple relationships. No table may contain two or more 1:N (one-to-many) or N:M (many-to-many) relationships that are not directly related.
Bocyce code normal from.
A relationship in bcnf, if n only if every determine is a
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candidate key.
The difference between 3 rd nf and bcnf is that for a functional
dependency a → b 3 rd nf allow this dependency in a relation b
is a primary key attribute in a attribute and a is not a candidate
key.
Where bcnf instance that for this dependency to remain in to
relation a must be candidate key.
B. Explain the concept of keys and their significance.
Ans: Key :
Key is a minimal set of attribute.
A key is an entity set such that number of two entities agrees
on all attribute.
A key is a data item of field which computer using to identify
to records database system which is refer two as keys.
A key is a single attribute or combination of attribute that is
use to identify one or more instance of the set.
There are eight (8) types of keys.
Primary key.
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Foreign key/reference key.
Super key.
Candidate key.
Composite key.
Alternate key.
Simple key.
Secondary key.
1.primary key :-
Primary key is a uniquely identification of column is in table.
Primary key has a tow rules given as bellow.
Primary key is a unique.
Primary key is not null.
A primary key is a field that uniquely identifies each record in the database.
When you declare primary key in your table then that table is
called parent table/prime table/main table.
If you can put key in a table then you see the little symbol of
key that particular field’s right side.
Example:
CUSTOMERS
CustomerNo FirstName LastName1 Sally Thompson2 Sally Henderson3 Harry Henderson4 Sandra Wellington
For example, in the table above, Customer No is the primary key.The values placed in primary key columns must be unique for each row: no duplicates can be tolerated. In addition, nulls are not allowed in primary key columns.E.g. of Primary Key - Database designer can use one of the Candidate Key as a Primary Key. In this case we have “Code” and “Name, Address” as Candidate Key, we will consider “Code” Key as a Primary Key as the other key is the combination of more than one attribute.
2. Foreign key/reference key:-
Foreign key/reference key is a relation of two or more table in
which you can take primary key field to another.
Table that referential integrity is created.
When you declare primary key in your table then that table is
called parent table/prime table/main table.
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When that primary key is reference in another that which is
called foreign key/reference table/child table/detail table.
If the data is exit in master table then n only then we can use in
child table
Example :-
Table 1:
Field 1 Field 2 Field 3
Reference way
Table 2:Field a Field b Field 1
See above example field 1 has a primary key in table 1 and that
field is again use in table 2 as a references is called a foreign
key/reference key
3. Super key :-
Super key is a set of each field of given table or subset of any
field of that given table.
In shrot,there is primary key in a simple table but when we are
describe that table then their described(subset) table have not a
primary key is called super key.
Example :-
My_emp{empid,ename,salary,doj,design,address};
Here, there is a give one table my_emp, and empid has a primary
key. Now we can describe the table given as below.
Field1{ename,salary,doj,address};
Field2{empid,ename};
Field3{salary, design};
When we are describe the simple table just like
field1,field2,field3 then which described(subset) table has a
primary key it’s not a super key or super table
Here, there are field1 & field3 have not primary key then it is a
super key or super table and field2 have a primary key then it
Primary key
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is not a super key or super table.
4.candidate key :-
Candidate key can be define as minimal super key in other
word in attribute a combination of attribute that identify that
record, uniquely but non of is proper subset can identify record
uniquely.
Candidate key has at least one primary key of described
(subset) table.
Candidate key is also super key but super key is not
candidate key.
Example :-
My_emp(empid,ename,salary,doj,design);
Here, there is a give one table my_emp, and empid has a primary
key. Now we can describe the table given as below.
Field1{empid,ename,salary,doj,address};
Field2{ename,salary};
Field3{empid,salary,design};
When we are describe the simple table just like
field1,field2,field3 then which described(subset) table have a
primary key is called candidate key or candidate table
Here, there are field1 & field3 have primary key then it is a
candidate key or candidate table and field2 have not primary
key then it is not a candidate key or candidate table.
Here all table is also know as super key or super table
5.composite key :-
Composite key is a set of two primary key in one table.
Here, you are confused that how it is possible because one
table have an only one primary key then how it is possible? It
confiscation’s answer is given as bellow through examples &
some brief information.
First a fall we can create two tables when the in a table have at
least one primary key and we can meagre that table in third
table as a reference key and that table is define as a composite
key or composite table.
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Example :-
Table 1:
Student(sid,sname,city,achievement,contactno);
Table 2:
Course(cid,cname);
Here, there are two tables and is have a primary key to field sid
and cid.
Now we are describing that table and create third table as
stu_course.
Table 3:
Stu_course(sid,cid);
See, here table 3 has a tow primary key before we can describe
that two tables as a stu_course and see table 1 have a primary
key as a sid and table 2 have a primary key as cid and when we
are describe that as a table 3 stu_course sid & cid is a primary
key as a reference key it is called a composite key.
6.alternative key :-
Alternative key can be any of the candidate key accepts for the
primary key.
Alternative key is a combination of that attributes of table have
a no composite key.
In short it is just like a candidate key but it is not candidate
key or super key.
Example :-
Table 1:
Student(sid,sname,city,achievement,contactno);
Table 2:
Course(cid,cname);
Here, there are two tables and is have a primary key field sid
and cid and other field are none selected in key that all are
define as alternative key.
Now we are describing that table and create third table as
stu_course.
Table 3:
Stu_course(sid,cid);
See, here table 3 has a tow primary key before we can describe
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that two tables as a stu_course and see table 1 have a primary
key as a sid and table 2 have a primary key as cid and when we
are describe that as a table 3 stu_course sid & cid is a primary
key as a reference key it is called a composite key.
Table 4:
Stu_cource1(sname,city,achiement,contactno,cname);
See, here there are not primary key in a table 4 it is called
alternative key or alternative table.
7.secondary key :-
The attribute that are not event the super key but can be still
use for identification of record not (unique) are know as
secondary key or secondary table.
In short table have a no primary key.
Their records are not uniquely or randomly.
Secondary key is working as an alternate of primary key.
Means secondary key is null.
Secondary key is not unique.
C. Explain the concept of database management system.
Ans DBMS: database management system.
Database: a systematic type of argument of related
information is called a database.
DBMS: Database management system is collection of
interrelated data and a set of program to access those data.
It is a collection of inter related data.
It is set of program to access the data
DBMS is a contain of information about a particular enterprise.
DBMS provide an environment that is both convenient and
efficient to use.
Goal of DBMS: DBMS is providing a way to store and relative
database information that is both convenient and efficient.
Database system application:
Banking.
Airlines.
Universities/schools
Credit card transitions.
Telecommunication.
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Finance.
Sales.
On-line retails.
Manufacturing.
Human resource.
Purpose of database system(drawback of file processing
system):
Data redundancy and inconsistency.
Difficulty in accessing data.
Data isolation.
Integrity problem.
Atomicity problem.
Concurrent-access anomalies.
Security problem.
Advantage of DBMS:
Data independency.
Efficient data.
Data administrator.
Concurrent & cress recovery.
Reduce application development time.
Feasibility.
Fast response to information request.
Multi access.
Lest store age.
Advantage of DBMS in brief:
Application program should be as independent as possible from
details of data representation and storage. The DBMS can
provide an abstract view of the data to insulate application
code form such detail.
A DBMS utilize avarety of sophisticated techniques to store
adretrive data efficiently. This feature is especially impotent if
the data is stored on external storage devices.
If data is always accessed through the DBMS, the DBMS can
enforce integrity constrain on the data for example before
inserting on the data for an employee.
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When several users share the data cartelization the
administrator of data can offer significant improvements.
Experienced professionals who understand the nature of data
being managed.
A DBMS schedules concurrent access tit hr data in such a
manner that user can think of the data as being accessed by
only one user.
Clearly the DBMS supports many important functions that are
common to many applications accessing store in the DBMS.
Q-5 Consider the following relations. 12.
Myemp(empno,ename,doj,sal,desig)
♫ create table myemp
(
Empno number primary key,
Ename text,
Doj text,
Sal currency,
Design text
);
Project(pcode,pname)
♫ create table project
(
Pcode text primary key,
Pname text
);
Emp_prog(pcode,empno)
♫ create table emp_prog
(
Pcode text references project(pcode),
Empno number references myemp(empno)
);
When we was a create table then we must be insert records and
when we insert records then we must be follow insert command
query it is given as below with example
Syntax :-
SEPTEMBER / OCTOBER-2009 [12BCA37,12BCA38,12BCA40]
Insert into <table name>
Values(value1,value2,value3,……value_n);
Example :-
Insert into myemp
Values(1,’abc’,’01-01-2001’,12000’programmer’);
Insert into project
Values(‘p001’,xyz’);
Insert into emp_prog
Values(‘p001’,’02’);
Ms access is a case sensitive then if you was wrote fields names in
upper or lower case and you may be use that field as a references
then you must be write in same name and same case.
Write a appropriate sql statement for the following :
1. Get the details of employees, whose designation start with an
alphabet ‘p’ and have length of more than 10 characters.
Ans:
2. Get the details of all employees whose designation are
“programmer” and not allocate any project.
Ans:
3. Get the name of an employees who is working on project ‘p001’
and ‘p002’ both
Ans:
4. Get the name of an employees working on project ‘p001’
Ans:
5. Get the details of employees who get minimum salary and
working on project ‘p001’
Ans: