Database system

1. Collecting Information
Task 3: Keys
and
Relationships

2. What does Primary Key mean?
Definition - A primary key is a special
relational database table column (or
combination of columns) designated to
uniquely identify all table records.
A primary key is used as a unique
identifier to quickly parse data within
the database and find the relation
between different tables. A relational
database cannot have more than one
primary key.

3. A primary key’s main features
are:
It must contain a unique value for
each row of data.
It cannot contain null values.
Every row must have a primary key
value.
A primary key is either an existing
table column or a column that is
specifically generated by the database
according to a defined sequence.

4. Collecting Information
identify a
primary key

5. How do you identify a primary
key?
The primary key consists of one or
more columns whose data contained
within are used to
uniquely identify each row in the table.
You can think of them as an address. If
the rows in a table were mailboxes,
then the primary key would be the
listing of street addresses.
https://www.youtube.co
m/watch?v=Py6F4vF5n
Primary
Key
Video

6. What is primary key and
example?
 A primary key is either an existing
table column or a column that is
specifically generated by the
database according to a defined
sequence. For example, students
are routinely assigned unique
identification (ID) numbers, and all
adults receive government-
assigned and uniquely-identifiable
Social Security numbers

7. What is the function of primary
key?
 The main purpose of a primary key is to
implement a relationship between two
tables in a relational database
Can a table have two primary
keys?
 A table can have only one primary key,
which may consist of single
or multiple fields. When multiple fields are
used as a primary key, they are called a
composite key. If a table has a primary
key defined on any field(s), then you
cannot have two records having the same
value of that field(s).

8. Is it mandatory for the primary key to
be given a value when a new record
is inserted?
Primary keys must contain
unique values. A primary key column
cannot have NULL values. ... If a table
has a primary key defined on any
field(s), then you cannot have
two records having the same value of
that field(s). Note − You would use
these concepts while creating database
tables.

9. ID FIELD

10. An identity column is a column (also
known as a field) in a database table that is
made up of values generated by
the database.
What is ID field?
Fields are elements in a table. ...
A field may be designated as a primary key,
where it has a unique value for each record,
is indexed, and identifies a record.
https://www.youtube.com/watch?v=kG5edDF
ilhw
ID FIELD

11. ID FIELD
 An ID field is normally designated as
a primary key, and it is usually placed
into a second table in order to create a
relationship between them.

12. Example of ID Field
 Admission no
 Registration No
 Employee No
 NIC (National Identity card Number).
 Student GR No

13. TABLE
RELATIONSHIPS

14. TABLE RELATIONSHIPS
 What are the 3 types of relationships
in a database?
 There are three types of relationships
between the data you are likely to
encounter at this stage in the design:
one-to-one, one-to-many, and many-
to-many. To be able to identify these
relationships, you need to examine the
data and have an understanding of
what business rules apply to the data
and tables

15. What is table relationship
in database?
 A relationship, in the context
of databases, is a situation that exists
between two relational database
tables when one table has a foreign key
that references the primary key of the
other table.
 Relationships allow
relational databases to split and store
data in different tables, while linking
disparate data items.

16. What is an example of a one to
one relationship?
A one-to-one relationship exists
when each row in one table has
only one related row in a second table.
For example, a business might decide
to assign one office to
exactly one employee.
Thus, one employee can have
only one office. The same business
might also decide that a department can
have only one manager

17. What is a many to one
relationship?
 A many-to-one relationship is
where one entity (typically a column or
set of columns) contains values that
refer to another entity (a column or set
of columns) that has unique values

18. What is the most common
type of relationship between
two tables?
one-to-many relationship
 A one-to-many relationship is
the most common
relationship found between tables in
a relational database.
 The following is an example of
a form used in a database to display
the data from two tables with a one-
to-many relationship.

19. Many-to-many relationships
https://fmhelp.filemaker.com › help › fmp ›
FMP_Help › many-to-many-r...
Many-to-many relationships. A many-to-
many relationship occurs
When multiple records in a table are
associated with multiple records in
another table. For example, a many-to-
many relationship exists between
customers and products: customers can
purchase various products, and products
can be purchased by many customers.

20. Collecting Information
Record &
Fields
In Database

21. What is a table record?
 In database, a table is a data
structure where data can be organized
in fields (columns) & records (rows).
For example, information of the
employees of an organization needs
to be stored. ... A record represents
set of related data. Complete set of
values for all column/field is
called record or row

22. What are the fields in a
database?
 In computer science, data that has
several parts, known as a record, can
be divided into fields. Relational
databases arrange data as sets of
database records, so called rows.
Each record consists of several fields;
the fields of all records form the
columns. Examples of fields: name,
gender, hair colour

23. What is record with example?
Records are composed of fields, each of
which contains one item of information. A
set of records constitutes a file.
 For example, a personnel file might
contain records that have three fields: a
name field, an address field, and a
phone number field. In relational
database management
systems, records are called tuples
• a data structure consisting of multiple
parts.

24. What is the difference between a
field and a record?
 Fields and records are two basic
components of a database, which is
an organized collection of information,
or data. The term "fields" refers to
columns, or vertical categories of data
while the term "records" refers to
rows, or horizontal groupings of
unique field data.


25. What is Field record and table in
database?
 Data is stored in records. A record is
composed of fields and contains all
the data about one particular person,
company, or item in a database. In
this database, a record contains the
data for one customer support incident
report. Records appear as rows in
the database table

26. What are fields in Excel?
 Each individual item of information in a
database record – such as a
telephone number or street number –
is referred to as a field.
 In Excel, the individual cells of a
worksheet serve as fields, since each
cell can contain a single piece of
information about an object

27. what is the difference between
database and table?
 Database: collection of organized
data and specific features to access
them. Organized means in the form
of tables, views and stored
procedures, functions etc to access
the data. Table : collection of Rows
and Columns to store the data

28. What is the relationship between
a database and a table?
 A database is a collection of
interrelated data , these data are
stored in the table which are related to
one another , to search and retrieve
data queries are made . A table is
made up of rows and columns , data
of databases are stored in the table

29. How is database related to a
table?
A table is a collection of related data
held in a table format within
a database. ... In relational databases,
and flat file databases, a table is a set
of data elements (values) using a model
of vertical columns (identifiable by
name) and horizontal rows, the cell
being the unit where a row and column
intersect.

30. Should all tables have a primary
key?
It is a good practice to have a PK on
every table, but it's not a MUST. ...
"PRIMARY KEY constraints identify the
column or set of columns
that have values that uniquely identify a
row in a table. No two rows in
a table can have the same primary
key value. You cannot enter NULL for
any column in a primary key

31. GOOD BYE