Import Package Error - Cannot Convert between Unicode and Non Unicode String Data Type

I have made a dtsx package on my computer using SQL Server 2008. It imports data from a semicolon delimited csv file into a table where all of the field types are NVARCHAR MAX.

It works on my computer, but it needs to run on the clients server. Whenever they create the same package with the same csv file and destination table, they receive the error above.

We have gone through the creation of the package step by step, and everything seems OK. The mappings are all correct, but when they run the package in the last step, they receive this error. They are using SQL Server 2005.

Can anyone advise where to begin looking for this problem?

The problem of converting from any non-unicode source to a unicode SQL Server table can be solved by:

• add a Data Conversion transformation step to your Data Flow
• open the Data Conversion and select Unicode for each data type that applies
• take note of the Output Alias of each applicable column (they are named Copy Of [original column name] by default)
• now, in the Destination step, click on Mappings
• change all of your input mappings to come from the aliased columns in the previous step (this is the step that is easily overlooked and will leave you wondering why you are still getting the same errors)

At some point, you're trying to convert an nvarchar column to a varchar column (or vice-versa).

Moreover, why is everything (supposedly) nvarchar(max)? That's a code smell if I ever saw one. Are you aware of how SQL Server stores those columns? They use pointers to where the column is stored from the actual rows, since they don't fit within the 8k pages.

Non-Unicode string data types:
Use STR for text file and VARCHAR for SQL Server columns.

Unicode string data types:
Use W_STR for text file and NVARCHAR for SQL Server columns.

The problem is that your data types do not match, so there could be a loss of data during the conversion.

Two solutions: 1- if the type of the target column is [nvarchar] it should be change to [varchar]

2- Add a "Derived Column" component to the SSIS package and add a new column with the following expression:
(DT_WSTR, «length») [ColumnName]

Length is the length of the column in the target table and ColumnName is the name of the column in the target table. finally at the mapping part you should use this new added column instead of the original column.

Not sure if this is a best practice with SSIS but sometimes I find their tools are a bit clunky when you want to do this type of activity.

Instead of using their components you can convert the data within your query

Instead of doing

SELECT myField = myNvarchar20Field
FROM myTable

You could do

SELECT myField = CONVERT(VARCHAR(20),myNvarchar20Field)
FROM myTable

This a solution that uses the IDE to fix:

1. Add a Data Conversion item to your dataflow as shown below;

2. Double click on the Data Conversion item, and set it as shown:

3. Now double click on the DB Destination item, Click on Mapping, and ensure that your input Column is actually the same as coming from the Copy of [your column name], which is in fact the Data Conversion output NOT the DB Source Output (be careful here). Here is a screenshot:

And thats it .. save and run ..

Mike, I had the same problem with SSIS in SQL Server 2005... Apparently, the DataFlowDestination object will always attempt to validate the data coming in, into Unicode. Go to that object, Advanced Editor, Component Properties pane, change the "ValidateExternalMetaData" property to False. Now, go to the Input and Output Properties pane, Destination Input, External Columns - set each column Data type and Length to match the database table it's going to. Now, when you close that editor, those column changes will be saved and not validated over, and it will work.

Follow the below steps to avoid (cannot convert between unicode and non-unicode string data types) this error

i) Add the Data conversion Transformation tool to your DataFlow.
ii) To open the DataFlow Conversion and select [string DT_STR] datatype.
iii) Then go to Destination flow, select Mapping.
iv) change your i/p name to copy of the name.

Get to the registry to configuration of the client and change the LANG. For Oracle, go to HLM\SOFTWARE\ORACLE\KEY_ORACLIENT...HOME\NLS_LANG and change to appropriate language.

The dts data Conversion task is time taking if there are 50 plus columns!Found a fix for this at the below link

http://rdc.codeplex.com/releases/view/48420

However, it does not seem to work for versions above 2008. So this is how i had to work around the problem

*Open the .DTSX file on Notepad++. Choose language as XML
*Goto the <DTS:FlatFileColumns> tag. Select all items within this tag
*Find the string **DTS:DataType="129"**  replace with **DTS:DataType="130"**
*Save the .DTSX file. 
*Open the project again on Visual Studio BIDS
*Double Click on the Source Task . You would get the message

the metadata of the following output columns does not match the metadata of the external columns with which the output columns are associated:
...
Do you want to replace the metadata of the output columns with the metadata of the external columns?

 *Now Click Yes. We are done !

Resolved - to the original ask:

I've seen this before. Easiest way to fix (don't need all those data conversion steps as ALL of the meta data is available from the source connection):

Delete the OLE DB Source & OLE DB Destinations Make sure Delayed Validation is FALSE (you can set it to True later) Recreate the OLE DB Source with your query, etc. Verify in the Advanced Editor that all of the output data column types are correct Recreate your OLE DB Destination, map, create new table (or remap to existing) and you'll see that SSIS got all the data types correct (same as source).

So much easier that the stuff above.

Not sure if this is still a problem but I found this simple solution:

1. Right-Click Ole DB Source
2. Select 'Edit'
3. Select Input and Output Properties Tab
4. Under "Inputs and Outputs", Expand "Ole DB Source Output" External Columns and Output Columns
5. In Output columns, select offending field, on the right-hand panel ensure Data Type Property matches that of the field in External Columns properties

Hope this was clear and easy to follow

Sometime we get this error when we select static character as a field in source query/view/procedure and the destination field data type in Unicode.

Below is the issue i faced: I used the script below at source

and got the error message Column "CATEGORY" cannot convert between Unicode and non-Unicode string data types. as below: error message

Resolution: I tried multiple options but none worked for me. Then I prefixed the static value with N to make in Unicode as below:

SELECT N'STUDENT DETAIL' CATEGORY, NAME, DATEOFBIRTH FROM STUDENTS
UNION
SELECT N'FACULTY DETAIL' CATEGORY, NAME, DATEOFBIRTH FROM FACULTY

If anyone is still experiencing this issue, I found that it related to a difference in Oracle Client versions.

I have posted my full experience and solution here: https://stackoverflow.com/a/43806765/923177

1.add a Data Conversion tool from toolbox
2.Open it,It shows all coloumns from excel ,convert it to desire output. take note of the Output Alias of
each applicable column (they are named Copy Of [original column name] by default)
3.now, in the Destination step, click on Mappings

I changed ValidateExternalMetadata=False for each transformation task. It worked for me.