Interested to Buy Any Domain ? << Click Here >> for more details...
Difference between primary key and unique key ?
- 77 Answers
- 210272 Views
- Accenture, B2B Software Technologies, Cognizant, HP Finsoft, IndiaNIC, Karomi Technology, Keane India Ltd, L&T, Onward eServices, R Systems, Shakti, Techtic Solutions, I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
Answer / dj
Primary key creates Clustered Index.
Unique key creates non-clustered Index
| Is This Answer Correct ? | 24 Yes | 4 No |
Answer / sreesakthi
primary key will not allow null values whereas unique key
will allow null values.we have only one primary key per
table,but we can have more than one unique key per table
| Is This Answer Correct ? | 25 Yes | 8 No |
Answer / pralhad
Each table having only one PRIMARY KEY.And my contain many
UNIQUE KEYS.
PRIMARY KEY is identity of each row. UNIQUE KEY also
identity of each row.
BOTH keys will not contain repeated value.
BUT UNIQUE KEY will contain NULL value but PRIMAY key will
not contain NULL value.
| Is This Answer Correct ? | 63 Yes | 47 No |
Answer / satendra dixit
Primary Key
1. Not Null
2. One primary key can be defined at on table
Unique Key
1. May be Null
2. one or more then 1, can be implemented
| Is This Answer Correct ? | 22 Yes | 11 No |
Answer / saurabh
the no of primary key in a table is one but the no of
unique is more then one
| Is This Answer Correct ? | 25 Yes | 15 No |
Answer / mohan singh
Primary key contain non repetitive value and not null
value,and primary key is created on clustered index.In the
table their should be one primary key column.
Unique key contain non repetitive value but can contain
only one null value in the column.And unique key is created
on non clustered index.
| Is This Answer Correct ? | 13 Yes | 3 No |
Answer / pankaj kumar tiwari
primary key create index it means its value inserted in
sequence but in unique, we insert data in any order
| Is This Answer Correct ? | 15 Yes | 6 No |
Answer / niraj pratap singh
primary key has no null values whereas unique accepts null
values and in a table only one primary key is declared
whereas unique key is multiple in a table.
| Is This Answer Correct ? | 10 Yes | 2 No |
Answer / rinu
1)unique key can be null but primariy key cant be null.
2)primariy key can be refrenced to other table as FK.
3)we can have multiple unique key in a table but PK is one
and only one.
4)PK in itself is unique key.
5)a table can have more then one unique key column but a
table can have only one primary key column.
6)primary key creates clustered index but unique key
creates non clustered index.
| Is This Answer Correct ? | 12 Yes | 7 No |
Answer / ela tiku
1. Primary key does not allow Nill value whereas Unique key
allows Null values.
2. There can more than one Unique key for a table however
there is only one primary key for ant tanle.
2. Whenever a primary key is assigned by default a
Clustered Index is created whereas When a Unique key is
created a Non Index clustered index is created...
| Is This Answer Correct ? | 8 Yes | 5 No |
Can we create more than one constraint to column ?
How do you bind variables in oracle?
What is an oracle cursor variable?
Give the advantages and disadvantages of clusters.
What is a deadlock ? Explain .
How to list all tables in your schema?
what is trigger?
Provide an example of a shell script which logs into SQLPLUS as SYS, determines the current date, changes the date format to include minutes & seconds, issues a drop table command, displays the date again, and finally exits.
what is null value?
What would you do with an in-doubt distributed transaction?
A table t is there.If you perform insert ,update and delete then the trigger will fire.What is the minimum no of trigger required for a table.
How to pass parameters to procedures in oracle?
Oracle General 
