2.9- Keys In Database And Types Of Keys- Super Key In ER Model In DBMS | keys in database
2.9- Keys And Types Of Keys- Super Key In ER Model In DBMS In Hindi | Super Key In DBMS
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A key is an attribute or set of attributes that is used to identify data in entity sets. The
attributes which are used as key are known as key attributes. Rest of all are known as
Non-key attributes.
2.6.1 Types of Keys
There are many keys that are used in the different tables. These are as follows:
1. Super Key : A super key is a set of collection of one or more than one attributes
that can identify data uniquely.
Any entity set has more than one super key.
Employee
Reg. No ID Name Salary Dept-ID
S1D 1 Mohan 1500 10
A25 2 Sohan 2000 30
33Z 3 Vikas 3000 20
Z4X 4 Madhu 1000 10
A5C 5 Sonal 5000 20
(a)
Department
Dept-ID Dept-Name
10 Sales
20 Marketing
30 Development
(b)
FIGURE 2.9. Entity sets employee and department.
Ex. In entity set Employee, shown in Figure 2.9(a), Super Keys are
(a) (ID, Name, Salary, Reg. No.)
(b) (ID, Name, Reg. No.)
(c) (ID) etc.
2.6- Degree Of Relationship Sets In ER Diagram In DBMS In Hindi | Binary & Ternary Relationship Set • Video
2.7- Mapping Constraints In ER Diagram In DBMS | Mapping Cardinality Or Cardinality Ratios In DBMS • Video
2.8- Participation Constraints In ER Diagram In DBMS In Hindi | Partial And Total Participation • Video Notes Link:
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