The document discusses database keys and their purpose in relational database management systems (RDBMS). Keys are fields that help create relationships between tables, maintain uniqueness within a table, and keep data consistent and valid. Primary keys uniquely identify each record in a table and do not allow null values or duplicate values. The example provided is an Employee_Id primary key in an Employee table.

1. The Relational Database Keys
Mrs. Sharmila K. Karpe
(shrmlkrp@gmail.com)
Assistant Professor, Dept of Information Technology
Walchand Institute of Technology, Solapur
(www.witsolapur.org)
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2. What is Key?
Walchand Institute of Technology, Solapur 2
Keys are fields in a table which participate in below activities in
RDBMS systems:
•To create relationships between two tables.
•To maintain uniqueness in a table.
•To keep consistent and valid data in database.
•Might help in fast data retrieval by facilitating indexes on
column(s).

3. Primary Key
.
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Primary key is a candidate key of the
table selected to identify each
record uniquely in table. Primary
key does not allow null value in the
column and keeps unique values
throughout the column.
example
Employee_Id is a primary key of Employee table.

4. References
Walchand Institute of Technology, Solapur
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Material references:
•Database System Concepts Avi Silberschatz Henry F. Korth S. Sudarshan
•http://www.sqlrelease.com/sql-server-tutorial/types-of-keys