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Relational data model is currently used in all business transactions. It is based on the concept introduced by E F Codd. It is composed of one or more tables. Tables are made up of rows and columns.

Here tables are called relations, rows are called tuples and the columns are called attributes. The advantages of this model is neither data redundancy nor complexity. 

Eg:

HTML is not an RDBMS package.

1.

2.

3. 

4. 

5.

With the help of DBMS the process of storing, retrieving and modifying data are greatly simplified.

Range checks and Value checks are the two types of integrity checks.

1. Candidate Key: 

It is a set of attributes that uniquely identifies a row. There may be more than candidate key and may be a combination of more than one attribute.

2. Primary Key: 

A primary key is one of the Candidate Keys. It is a set of one or more attributes that can uniquely identify tuples in a relation. 

3. Alternate Key: 

The Candidate key that is not the primary key is called the alternate key. 

4. Super Key: 

A combination of a primary key with any other attribute or group of attributes is called a super key. 

5. Foreign Key: 

A single attribute or a set of attributes, which is a candidate key in another table, is called foreign key.

1. Candidate Key: It is a set of attributes that uniquely identifies a row. There may be more than candidate key and maybe a combination of more than one attribute. 

2. Primary Key: A primary key is one of the Candidate Keys. It is a set of one or more attributes that can uniquely identify tuples in a relation. 

3. Alternate Key: The Candidate key that is not the. primary key is called the alternate key. 

4. Super Key: A combination of a primary key with any other attribute or group of attributes is called a super key. 

5. Foreign Key: A single attribute or a set of attributes, which is a candidate key in another table, is called foreign key.

Packages such as Oracle, My SQL, etc.

With the help of  DBMS the process of storing, retrieving and modifying date are greatly simplified.

Intersection operation. 

FOOTBALL ∩ CRICKET.

There is a standard BIS (Bureau of Indian Standards) in the field of Gold and ISBN (International Standard Book Number) in the field of publication. Similarly here is also some standards like ANSI(American National Standards Institute), ISO (International Organization for standardization), etc..

For example a led “Name” should have 40 characters is a standard.

Cardinalty of table T₁ is 10 means it has 10 rows Cardinalty of table T₂ is 8 means it has 8 rows Normally T₁ ∪ T₂ is 10 + 8 = 18 But Here T₁ ∪ T₂ is 13 means after eliminating duplication of 5 rows this happened.

This means 5 rows are common. That is T₁ ∩ T₂ is 5.

If Redunancy is controlled , DBMS can guarantee that database is never inconsistent.

Instead of storing more than one copy of the same data, it stores only one copy. This can be shared by several users. If redundancy occurs there is a chance to inconsistency. If redundancy is removed then in-consistency cannot occur

A relational database developer refers to a record as tuple.

(c) three level

If Redundancy is controlled , DBMS can guarantee that database is never inconsistent.

DBML is the language  that enables user to access or manipulate data as organized by RDBMS.

Data Independence – It is the ability to modify the scheme definition in one level without affecting the scheme definition at the next higher level. 

(a) Physical Data Independence – It is the ability to modify the physical scheme without causing application programs to be rewritten. 

(b) Logical Data Independence – It is the ability to modify the logical scheme without causing application programs to be rewritten.

CRICKET – FOOTBALL

(a) Degree(CD) - the number of Columns is the Degree Cardinality (RC)-: the number of Rows is the Cardinality T1 ∪ T2 = Sum of cardinalities of Table 1 and Table 2 i. e.T1 ∪ T2 = 10 + 8 = 18

(b) T1 ∩ T2 is the common rows(tuples) in T1 and T2 If there is no common tuples then T1 ∩ T2 is 0 hence the cardinality is 0.

In a relational model, relations are termed as tables. 

(b) data record

The property of a DBMS that guarantees that the database is never inconsistent Redundancy.

a) 

b)

c)

Field: Smallest unit of data. 

Eg: RolINo, Name 

Record: Collection of related fields. 

Eg: The information of a particular student. 

File: Collection of related records. 

Eg: The information of 10 students.

A Database is a collection of large volume of data. 

Advantages of DBMS

Data Redundancy – It means duplication of data. DBMS eliminates redundancy. DBMS does not store more than one copy of the same data.

Inconsistency can be avoided – If redundancy occurs there is a chance to inconsistency. If redundancy is removed then inconsistency cannot occur. Efficient data access It stored huge amount of data efficiently and can be retrieved whenever a need arise.

Data can be shared – The data stored in the database can be shared by the users or programs. 

Standards can be enforced – The data in the database follows some standards.

Eg: a field ‘Name’ should have 40 characters long. Some standards are ANSI, ISO, etc.

Security restrictions can be applied – The data is of great value so it must be kept secure and private. Data security means the protection of data against accidental or intentional disclosure or unauthorized destruction or modification by unauthorized person.

Integrity can be maintained – It ensures that the data is to be entered in the database is correct.

Crash recovery- Sometimes all ora portion of the data is lost when a system crashes . A good DBMS helps to recover data after the system crashed.

(a) Hierarchical Data Model 

(b) In relational data model data are stored as tables. Here the term relation means table. A table consists of rows and columns. Columns mean attributes and rows means tuples.

(a)  π_{name, address} (σ city_name = "kochi"(Hotel))

(b)  π_city__name(σ state = "kerala"(city))

(c)  π_name(Hotel)

(d)  π_name(σ city_name = "kozhikodi"V city_name = "Munnar"(Hotel))

Database Administrators (DBA) are more concerned with level Logical level of Abstraction.

(a) – (ii), (b) – (iii), (c) – (i)

Conceptual level is the other name for logical level

(c) Integrity

(b) data record

(d) view level

Physical – logical – view level. 

(how data) (what data) (view data) 

Physical Level is the lowest level. It describes how the data is actually stored in the storage medium. At physical level complex, low-level data structures are described in detail. 

Logical level describes what data are stored in the database and what relationships exist among data. Here database is described in terms of simple structure. Records are defined in this level. Programmers work at this level. 

View level is the highest level of data abstraction. It is concerned with the way in which the users view the database. It describes only part of the database.

Select – unary operator.

Answer is (a) Create

Select – unary operator.

Attributes- These are column names, i.e, Emp_Code, Name, Department, Designation and Salary Degree(CD) - the number of Columns is the Degree i. e Degree is 5(Here 5 columns)

Cardinality (RC)-: the number of Rows is the Cardinality i. e. Cardinality is 4(Here 4 rows) Domain is the pool of possible values Domain of Name is a String(Sudheesh, Dhanya, Fathima, Shajan.etc) Domain of Emp_Code is a number (1000,1001,1002, 1003, etc)

(a) Reg_no and Reg_no+Batch are the candidate keys. We set Reg_no as the primary key hence Reg_no+Batch is the alternate key 

(b) Candidate Key :

It is a set of attributes that uniquely identifies a row. There may be more than candidate key and may be a combination of more than one attribute.

Primary Key:

A primary key is one of the Candidate Keys. It is a set of one or more attributes that can uniquely identify tuples in a relation.

(a)

(b)

Correct answer is (c) Integrity

As part of project work, Ashish denes the type of data and the relationship among them. He is at Logical level of database abstraction.

Logical level

Advantages of DBMS 

1. Data Redundancy – It means duplication of data. DBMS eliminates redundancy. DBMS does not store more than one copy of the same data.

2. Inconsistency can be avoided – If redundancy occurs there is a chance to inconsistency. If redundancy is removed then inconsistency cannot occur.

3. Data can be shared – The data stored in the database can be shared by the users or programs.

4. Standards can be enforced – The data in the database follows some standards. Eg: a field ‘Name’ should have 40 characters long. Some standards are ANSI, ISO, etc.

5. Security restrictions can be applied – The data is of great value so it must be kept secure and private. Data security means the protection of data against accidental or intentional disclosure or unauthorized destruction or modification by unauthorized persons.

6. Integrity can be maintained – It ensures that the data is to be entered in the database is correct. 

7. Efficient data access – It stored huge amount of data efficiently and can be retrieved whenever a need arise. 

8. Crash recovery – Some times all or a portion of the data is lost when a system crashes. A good DBMS helps to recover data after the system crashed.

Physical level.

a – iv 

b – iii 

c – i.

(d) view level