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C# primary key

Posted on 2016-10-04
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Last Modified: 2016-10-05
I would like to create unique identifier like below.

1. h111111

the format is
1. Must start "h"
2. with 5 numbers only

the 5 numbers can be random, but once it is created, it can't be duplicated.

is it possible?
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Question by:ITsolutionWizard
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9 Comments
 
LVL 29

Expert Comment

by:Pawan Kumar
ID: 41829212
Yes possible..

SQL Solution , try

SELECT CONCAT( 'h' , RIGHT(RAND(),5) )
0
 
LVL 29

Expert Comment

by:Pawan Kumar
ID: 41829213
One more option for < SQL Server 2012

SELECT 'h' + CAST(CONVERT(NUMERIC(12,0),RAND() * 99999) + 10000 AS VARCHAR(7))
0
 
LVL 11

Expert Comment

by:HuaMinChen
ID: 41829228
By Unique constraint to the column, you can achieve this.
0
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LVL 23

Expert Comment

by:Rajkumar Gs
ID: 41829231
Since you have to generate next ID in a custom format, better go for sequence approach to make sure no duplicates.
Try any of the explained approach here
http://www.sqlteam.com/article/custom-auto-generated-sequences-with-sql-server
0
 
LVL 1

Author Comment

by:ITsolutionWizard
ID: 41829239
Can we use it without sql?
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LVL 29

Accepted Solution

by:
Pawan Kumar earned 2000 total points
ID: 41829278
Try below options..

Random rnd = new Random();
        string str1 = "H" + rnd.Next().ToString().Substring(0, 5);


        char[] ch = Guid.NewGuid().ToString().Where(x => char.IsNumber(Convert.ToChar(x))).Take(5).ToArray();
        string str2 = "H" + (new string(ch));

--

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Enjoy!!
0
 
LVL 29

Expert Comment

by:Pawan Kumar
ID: 41829344
Yes you can also create unique constraints..Approach below.

DataTable at ;

UniqueConstraint aUnique =  new UniqueConstraint(
new DataColumn[] { at.Columns["ID"], at.Columns["Name"] });

at.Constraints.Add(aUnique);
0
 
LVL 51

Expert Comment

by:Vitor Montalvão
ID: 41829376
the 5 numbers can be random, but once it is created, it can't be duplicated.
Choose one of the above solutions to implement the generation of the values but to assure that's no duplicates you'll need to create an unique index on the field:
CREATE UNIQUE INDEX IndexName ON TableName (ColName)

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or create a Primary Key if you don't have one in the table:
ALTER TABLE TableName  
ADD CONSTRAINT PK_TableName_ColName PRIMARY KEY (Colname)

Open in new window

1
 
LVL 1

Author Closing Comment

by:ITsolutionWizard
ID: 41831144
This is the best solution. Without using SQL is perfect. Good Job
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