How to compare text columns

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How to compare text columns

Steve Harp

Old Hand

Points: 321
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December 23, 2006 at 11:12 am

#114985

Hi All,
I have a table that stores ASCII text in a column of type text in a SQL 2000 database. I need to compare new records with existing in order to avoid duplicate entries. The table has slightly over 20,000 records and grows at a rate of about 15-20 records per day.
I understand that SQL Server 2000 doesn't allow something like
if (NOT Exists(Select ID from the_table where the_text = the_text))
How can I compare text columns to avoid duplicates?
Thanks,
Steve

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DiMac SSC Veteran Points: 215 More actions · Answer 1

Have you tried this script in the library:

http://www.sqlservercentral.com/scripts/viewscript.asp?scriptid=1527

Cheers,

Diane

Steve Harp Old Hand Points: 321 More actions · Answer 2

Thanks for your response Diane but I don't think this is giving me what I need. Of the 20,000+ records in this table, only about 14,000 are unique. However, using the function generated by the script you suggested creates an interger value which is unique for each record. In other words, it doesn't identify any duplicates in the table.

select distinct dbo.fn_CheckSum_Text(my_text) from my_table

returns every record in the table.

Am I doing something wrong or is there another way check text fields to ensure that duplicate records are prevented?

Steve

schleep SSChampion Points: 12585 More actions · Answer 3

Not especially efficient, but you can do

WHERE CHARINDEX(, ) = 1

schleep SSChampion Points: 12585 More actions · Answer 4

Hmmn, I put the greater-than / less-than brackets in last post, they were stripped out....

WHERE CHARINDEX(The_Text, TextCol) = 1

Dave G-297451 SSC Journeyman Points: 95 More actions · Answer 5

I assume that the text you are comparing could be greater then 8000 char. If not, a redefinition to varchar(8000) could solve your problem.

or you could compare the first 8000 char using substring

Steve Harp Old Hand Points: 321 More actions · Answer 6

Some of the records are considerably more than 8,000 characters .

john-132685 SSCertifiable Points: 6134 More actions · Answer 7

Then you could always break the statement into multiple filters

where substring(a.text, 1, 8000) = substring( b.text, 1, 8000)

and substring(a.text, 8001, 8000) = substring( b.text, 8001, 8000)

and substring(a.text, 16001, 8000) = substring( b.text, 16001, 8000)

(dont forget the isnull around each or a check that datalength of each is right for substring size)