2. RELATIONAL DATABASE
• A relational database is a type of database that stores
and provides access to data points that are related to
one another.
• Relational databases are based on the relational
model, an intuitive, straightforward way of
representing data in tables.
• In a relational database, each row in the table is a
record with a unique ID called the key.
• The columns of the table hold attributes of the data,
and each record usually has a value for each attribute,
making it easy to establish the relationships among
data points.
3. RELATIONAL DATABASE
What is RDBMS?
• RDBMS stands for Relational Database Management System.
• RDBMS is the basis for SQL, and for all modern database
systems like MS SQL Server, IBM DB2, Oracle, MySQL, and
Microsoft Access.
• A Relational database management system (RDBMS) is a
database management system (DBMS) that is based on the
relational model as introduced by E. F. Codd.
4. RELATIONAL DATABASE
Relational database terms:
Tables
• The data in an RDBMS is stored in database
objects which are called as tables. This table is
basically a collection of related data entries
and it consists of numerous columns and
rows.
5. RELATIONAL DATABASE
Field:
• Every table is broken up into smaller entities called
fields. The fields in the CUSTOMERS table consist of
ID, NAME, AGE, ADDRESS and SALARY.
• A field is a column in a table that is designed to
maintain specific information about every record in
the table.
6. RELATIONAL DATABASE
Record or a Row:
• A record is also called as a row of data is each
individual entry that exists in a table.
Column:
• A column is a vertical entity in a table that contains
all information associated with a specific field in a
table.
7. RELATIONAL DATABASE
NULL value:
• A NULL value in a table is a value in a field that
appears to be blank, which means a field with a NULL
value is a field with no value.
• It is very important to understand that a NULL value
is different than a zero value or a field that contains
spaces. A field with a NULL value is the one that has
been left blank during a record creation.
8. RELATIONAL DATABASE
ADVANTAGES & DISADVANTAGES
• Advantages:
1. Ease of use: The revision of any information as tables consisting of rows
and columns is much easier to understand .
2. Flexibility: Different tables from which information has to be linked and
extracted can be easily manipulated by operators such as project and join to
give information in the form in which it is desired.
3. Precision: The usage of relational algebra and relational calculus in the
manipulation of he relations between the tables ensures that there is no
ambiguity, which may otherwise arise in establishing the linkages in a
complicated network type database.
9. RELATIONAL DATABASE
4. Security: Security control and authorization can also be implemented more
easily by moving sensitive attributes in a given table into a separate relation
with its own authorization controls. If authorization requirement permits, a
particular attribute could be joined back with others to enable full
information retrieval.
5. Data Independence: Data independence is achieved more easily with
normalization structure used in a relational database than in the more
complicated tree or network structure.
6. Data Manipulation Language: The possibility of responding to query by
means of a language based on relational algebra and relational calculus e.g
SQL is easy in the relational database approach. For data organized in other
structure the query language either becomes complex or extremely limited in
its capabilities.
10. RELATIONAL DATABASE
• Disadvantages :
1. Performance: A major constraint and therefore disadvantage in the use of
relational database system is machine performance. If the number of tables
between which relationships to be established are large and the tables
themselves effect the performance in responding to the sql queries.
2. Physical Storage Consumption: With an interactive system, for example an
operation like join would depend upon the physical storage also. It is,
therefore common in relational databases to tune the databases and in such
a case the physical data layout would be chosen so as to give good
performance in the most frequently run operations. It therefore would
naturally result in the fact that the lays frequently run operations would tend
to become even more shared.
3. Slow extraction of meaning from data: if the data is naturally organized in a
hierarchical manner and stored as such, the hierarchical approach may give
quick meaning for that data.
