MATLAB: Do I receive an error ” The conversion from UNKNOWN to NCHAR is unsupported” when working with DATAINSERT or FASTINSERT in Database Toolbox 3.10 (R2012a)

Database Toolbox

I am trying to insert data into my database using:

datainsert(con,'myTable',{'myColumn'},{'A'});

This throws the following error however: ERROR: Error using database/datainsert (line 129) Unable to insert element in row 1 column 1, A. The conversion from UNKNOWN to NCHAR is unsupported.

Best Answer

Support for inserting characters t ypes has been incorporated in Release 2012b (R2012b). For previous product releases, read below for any possible workarounds:

There is a limitation in Database Toolbox 3.10 (R2012a) in the way that it does not support nchars containing only one character.

To work around this limitation please install the attached patch:

1. Log in to an account with appropriate permissions to overwrite files in your MATLAB installation. On Linux systems, this is typically the root account.

2. Locate your MATLAB installation by typing matlabroot at the MATLAB command prompt. This folder is referred to as <MATLAB> in subsequent steps.

3. Exit MATLAB.

4. Download the attached .zip file associated with this Bug Report and store the file in the <MATLAB> folder.

5. Make a backup copy of each of the files listed in the .zip file. To see the contents of the .zip file open the .zip file in Winzip or Linux equivalent and look at the contents.

6. Extract the files from the .zip file.

a. Open the .zip file.

b. Extract the contents of the file to your <MATLAB> folder.

7. Delete the .zip file in the <MATLAB> folder.

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The following code, returns a struct containing only the subfolders of a folder.

% get the folder contents
>> d = dir('foldername')
% remove all files (isdir property is 0)
>> dfolders = d([d(:).isdir]) 
% remove '.' and '..' 
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MATLAB: Do I see a “java.lang.NullPointerException” in the installation log when trying to install a support package

The support package installation folder is not set or cannot be retrieved for some reason. The installation folder is saved in $MATLAB/toolbox/local/supportpackagerootsetting.xml. The file may not exist, not have read permissions or be invalid.

Run the following command to see if any errors are returned:

>> matlabshared.supportpkg.getSupportPackageRoot

Run the following to set an installation folder, then run the above again to verify if the folder was set properly:

>> matlabshared.supportpkg.setSupportPackageRoot('path_to_writable_location')

Replace "path_to_writable_location" with a valid path. Common locations are:

- Windows: C:\ProgramData\MATLAB\SupportPackages\<release>

- Linux: /home/<user>/Documents/MATLAB/SupportPackages/<release>

- Mac: /Users/<user>/Documents/MATLAB/SupportPackages/<release>

Alternatively, setting the contents of supportpackagerootsetting.xml to the following should work on all platforms:

<?xml version="1.0" encoding="UTF-8"?>
<SupportPackageRootSettings>
   <Setting name="sproot">__DEFAULT__</Setting>
</SupportPackageRootSettings>

Best Answer

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MATLAB: Do I see a “java.lang.NullPointerException” in the installation log when trying to install a support package