Basics - what is the difference between primary key, unique key, sorrougate key?

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what is the difference between primary key, unique key, sorrougate key?

Total Answers and Comments: 43

Last Update: November 13, 2009

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Best Rated Answer

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Submitted by: suresh

primaruy key should not dontain nulls and
unique key can contains null values

Above answer was rated as good by the following members:
exilant123, prashantmirje2000, divya.alw

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August 16, 2005 09:43:49

nagaa

RE: what is the difference between primary key, unique key, sorrougate key?

what is the difference b/w rownum and rowid?

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August 25, 2005 16:23:38

Nimi

RE: what is the difference between primary key, unique key, sorrougate key?

To answer your question its sufficient enough to understand their definitions.

Primary Key: A column in a table whose values uniquely identify the rows in the table. A primary key value cannot be NULL.

Unique Key: Unique Keys are used to uniquely identify each row in an Oracle table. There can be one and only one row for each unique key value.

Surrogate Key: A system generated key with no business value. Usually implemented with database generated sequences.

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August 26, 2005 13:38:02

Archit Dave

RE: what is the difference between primary key, unique key, sorrougate key?

i have one question is that

what are the differences between primary key and unique key

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August 27, 2005 00:52:49

vandita

RE: what is the difference between primary key, unique key, sorrougate key?

we can refer the primary key value in some other table ie child table.

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August 27, 2005 03:36:56

suresh

RE: what is the difference between primary key, unique key, sorrougate key?

primaruy key should not dontain nulls and
unique key can contains null values

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September 20, 2005 09:33:02

Vijay Raj Jaiswal

RE: what is the difference between primary key, unique...

Primay Key Unique key

----------- ------------------

1.There is only one there may be more than 1
Primary key for Unique Key in table
1 table

2.It can contain It Can contain Null Value
Null value

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September 30, 2005 02:42:29

gomathi.e

RE: what is the difference between primary key, unique...

unique key - allowes NULL ValuesPrimary Key - not allowed The NULL values

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October 16, 2005 03:14:57

chandrakant

RE: what is the difference between primary key, unique key, sorrougate key?

nagaa Wrote: what is the difference b/w rownum and rowid?

what is the difference between primary key unique key sorrougate key?

3how

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October 18, 2005 04:57:59

PSRaja

RE: what is the difference between primary key, unique...

send me the differences bet unique key & primary key

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November 23, 2005 01:58:08

#10

santhi

RE: what is the difference between primary key, unique...

both primary key and unique key doesn't have duplicate values. but there will be only primary key in a table and u can have any number of unique keys.

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