Super Key
Super key is a set of one or more attributes in a table that can uniquely identify each record present in a table.
A Super key may have additional attributes not needed for unique identification.
Aptitude
- Introduction
- File System vs DBMS
- Tuple
- Record
- Architecture
- Need of DBMS
- DBMS Abstraciton and Indipendence
- Data Models
- ER Models
- RDBMS
- Relational Data Model
- SQL Introduction
- SQL Types
- DDL Commands
- DQL Commands
- DML Commands
- DCL Commands
- TCL Commands
- Default Constraints
- Check Constraint
- Not Null Constraint
- Unique Constraint
- Key Constraint
- Key In DBMS
- Primary Key
- Foreign Key
- Super Key
- Candidate Key
- Alternate Key
- Composite Key
ER Models
RDBMS
SQL
SQL Constraints
Keys In DBMS
Super Key in DBMS
Example of the super key
| ID | NAME | PHONE | AGE |
|---|---|---|---|
| 66 | John | 7832973477 | 23 |
| 67 | Judy | 9732867464 | 21 |
| 68 | Elena | 8923826476 | 25 |
| 69 | John | 7326247844 | 23 |
The possible set of SuperKeys –
[ID]
As no two students will have the same Id, it will help to uniquely access the student details, hence it is a super key. Now we will identify all the Super Keys present in the table that is the set of attributes that will help to uniquely access a record
[NAME,ID]
Even if more than one student has the same name then the combination name will help to recognize the record, as student id will break the tie and this is combination is a super key
[PHONE ]
As no two students will have the same phone number, a phone number will help to uniquely access the student details and hence phone number is a super key
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