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sql_2k
Starting Member
26 Posts |
 Posted - 2008-03-05 : 05:16:42
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| Hi, Is there any datatype that cann't be used for Primary key column in a DB table. |
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SwePeso
Patron Saint of Lost Yaks
30421 Posts |
Posted - 2008-03-05 : 05:20:48
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TEXT, NTEXT and IMAGE.Try for yourself.DECLARE @Sample TABLE ( MyColumn TEXT PRIMARY KEY -- Change datatype and try! )
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elancaster
A very urgent SQL Yakette
1208 Posts |
Posted - 2008-03-05 : 05:33:55
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of course there's a difference between what CAN'T be used and what SHOULDN'T be used  what did you have in mind?Em |
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sql_2k
Starting Member
26 Posts |
Posted - 2008-03-05 : 05:54:08
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I would appreciate if you also let me know what datatype shouldn't be used for primary -key column.quote:
Originally posted by elancaster
of course there's a difference between what CAN'T be used and what SHOULDN'T be used what did you have in mind?Em
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elancaster
A very urgent SQL Yakette
1208 Posts |
Posted - 2008-03-05 : 06:00:52
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| it really depends on your requirement as to what makes a good / bad primary key.there's nothing really stopping you making a 'bit' column a primary key for example, but would you really want to? or varchar(8000) for example?Em |
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Jeff Moden
Aged Yak Warrior
652 Posts |
Posted - 2008-03-05 : 23:00:02
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| VARCHAR(8000) would make a really bad primay key ... ;-)--Jeff Moden |
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sql_2k
Starting Member
26 Posts |
Posted - 2008-03-06 : 03:24:13
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This is true, It depends on requirement to decide a good primary key.What I wanted to know - In DB table we have a coulmn of varchar(10) type which should be unique. But for easy handling I have added another identity primary key column to the table. So what I wanted to understand, as the varchar column uniquely identifies, so shall we go for making it as p-key or is it advisable to uphold another coulmn of int/identity type as primary key.quote:
Originally posted by Jeff Moden
VARCHAR(8000) would make a really bad primay key ... ;-)--Jeff Moden
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SwePeso
Patron Saint of Lost Yaks
30421 Posts |
Posted - 2008-03-06 : 03:49:40
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You can only have one primary key on a table.But you can have several UNIQUE constraints or indexes on a table.
E 12°55'05.25"N 56°04'39.16" |
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Primary Key DataType