Define the terms primary key foreign key and also the
difference between primary and the unique key
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Answer / pugal
Primary Key : The primary key of a relational table
uniquely identifies each record in the table
Foreign Key : These keys are used to create relationships
between tables.
Unique Key : In relational database design, a unique key is
a candidate key to uniquely identify each row in a table. A
unique key comprises a single column or set of columns
Difference between primary and unique key :
primary key not allows null values
unique key allows null values
| Is This Answer Correct ? | 33 Yes | 12 No |
Answer / nithya
one more difference is:
a table can have only one primary key but many unique keys.
| Is This Answer Correct ? | 22 Yes | 3 No |
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