checking for to make sure new record does not have a duplicate field in database.

[michaelxcampbell]

I am creating a new record in a database. I want to be able to check that a field does not have a duplicate entry in the database how do I do that and make sure that a duplicate record is not created

[Jay Talbott]

Re: checking for to make sure new record does not have a duplicate field in database.

The short answer is that you use the Server Side Event called CanInsertRecord to test if the duplicate entry exists. If it does, you prevent the insertion and let the user know that the record was not inserted.
You can do that with an ajax callback when the user leaved the field before they even try to submit the record if you want to.
We will need more info from you before we can give more details.
Jay

[michaelxcampbell]

Re: checking for to make sure new record does not have a duplicate field in database.

Thanks for the quick response Jay.
I have a simple form with 3 fields on it. One of the fields is an email address I want to check that entry against the database. What other information do you need?

[kingcarol]

Re: checking for to make sure new record does not have a duplicate field in database.

Will your database object to the duplicate with an error message? If so, I have been using the Server Side event onSQLExecuteError to capture the error when the user submits. You need to know the text of part of the error and put it in quotes in the atc statement. I also check mark to 'Show Row Errors in Pop Up Window' under Update Settings. This produces a nice pop up box with the message.

Here's a short video showing the code below in action: http://screencast.com/t/BN6J48KJ

Here's the code I was using:

function OnSQLExecuteError as c (e as p)

'Duplicate JOB_MAIN_CODE entered
if atc("1605 - '[Microsoft][ODBC Microsoft Access Driver] The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship.",e.errorMessage) > 1 then
	OnSQLExecuteError = "The Group Code entered has already been used.  Please enter a different Group Code."
	exit function
end if

'Setting return value to blank will use the default error message
OnSQLExecuteError = ""

end function

[kingcarol]

Re: checking for to make sure new record does not have a duplicate field in database.

AND, if your database will allow the duplicate, but you do not want it to... I have had to deal with that also. In the video in previous post, I also want to prevent a duplicate Group Title, but my database will allow it, so the following code in canUpdateRecord event (and similar code in canInsertRecord) takes care of it:

function CanUpdateRecord as v (DataSubmitted as P, Args as p, PageVariables as p, Result as p )
'debug(1)
with PageVariables

'per Selwyn, since OldDataSubmitted is not available in the CanUpdateRecord event, 
'you can get the old data submitted this way:
dim olddata as P
olddata = eval("pageVariables.old.v.r" + pageVariables._rowSubmitted)
'----------------------------------------------------------------------------------
'THIS BLOCK CREATED:  June 22, 2011
'CREATED BY:  Carol King
'PURPOSE - To do a lookup to see if the Group Heading (JOB_MAIN_DESC field) entered is a duplicate.
'If it is a duplicate, cancel the update and give user a message.

'If the user doesn't change the MAIN_CODE_DESC, we don't need to do check whether its a duplicate,
'and we want to make sure we don't prevent the correct error about a duplicate JOB_MAIN_CODE.
'So only execute the lookup code if there HAS been a change to the MAIN_CODE_DESC.
If olddata.MAIN_CODE_DESC <> DataSubmitted.MAIN_CODE_DESC then

	dim cn as sql::connection
	dim cs as c 
	cs = your connection string
	
	dim flag as l 
	flag = cn.open(cs)
	if flag = .f. then 
		Result.Cancel = .t.
		Result.ErrorHTML = "Could not connect to database. Error reported was: " + cn.CallResult.text
		exit function
	end if 
		
	sql = "select count (*) from TblMainJobCodes where JOB_MAIN_CODE <> :whatMainCode and MAIN_CODE_DESC = :whatHeading"
	dim args as sql::arguments
	args.add("whatHeading", DataSubmitted.MAIN_CODE_DESC)
	args.add("whatMainCode", DataSubmitted.JOB_MAIN_CODE)
	
	flag = cn.Execute(sql,args)
	if flag = .f. then 
		cn.Close()
		Result.Cancel = .t.
		'Capture the error that will cause query not to execute
		'if user entered data of a mismatched type for the fields.
		if atc("3030 - '[Microsoft][ODBC Microsoft Access Driver] Data type mismatch in criteria expression.",cn.CallResult.text) > 1 then
			Result.ErrorHTML = "The data type used in one of the fields does not match.  NOTE that the Group Code must be a number."
		else
			Result.ErrorHTML = "Could not execute query to detect duplicates in the CanUpdateRecord event. Error reported was: " + cn.CallResult.text
		end if
		
		exit function
	end if
		
	dim rs as sql::resultset
	rs = cn.ResultSet
	
	dim recordCount as n
	recordCount = rs.data(1)
	if recordCount >0 then 'a duplicate group heading was found
		cn.close()
		Result.Cancel = .t.
		Result.ErrorHTML = "The Group Heading entered is a duplicate of another one.  Please correct this and try again.  Or Cancel your entry."
		exit function
	else
		cn.close()
	end if
	
end if
'-----------------------------------------------------------------------------
'if we get to here, the update will not be cancelled.
Result.Cancel = .f.
Result.ErrorHTML = ""

end with

end function

[chadbrown]

Re: checking for to make sure new record does not have a duplicate field in database.

You can also use the field rules cross file validation which is very easy to use. Which will throw an error right on the field being entered incorrectly.

[kingcarol]

Re: checking for to make sure new record does not have a duplicate field in database.

You can also use the field rules cross file validation which is very easy to use. Which will throw an error right on the field being entered incorrectly.

Sounds great, Chad, but where is that field rule? I don't see it?

[chadbrown]

Re: checking for to make sure new record does not have a duplicate field in database.

Here you go.fieldrules.JPG

[kingcarol]

Re: checking for to make sure new record does not have a duplicate field in database.

Well, THANK YOU, Chad! I have been using the Validation for other things, and just didn't realize what 'cross file validation' meant so ignored it. I just tested it with value must NOT EXIST and it worked beautifully. Well, how simple is that? This is like playing some video game where you have to know which secret door to look behind.

[michaelxcampbell]

Re: checking for to make sure new record does not have a duplicate field in database.

Thank both of you for the help. Chad I got it setup and working using your suggestions
Thanks a bunch

[chadbrown]

Re: checking for to make sure new record does not have a duplicate field in database.

With Alpha there are oh so many doors. Glad to help.