Wrong Documentation? Convert to/from NULL value in Database

Wrong Documentation? Convert to/from NULL value in Database


hi referring to this thread:


Is it possible that the documentation on "Convert to/from NULL value in Database" is a typo?

Thank you


Both links are the same. Can you explain better what are you asking?



Yes Sir,

# i use external db mysql

# in a table coumn i give default value -999

# i choose the option "convert null to/from database" for the defaukt value"s behavior 

# when i insert value -999 it is inserted as null (as told in the document)

# however when i read back that null, it returns 0 (whether the document said it should return -999?)

Thank you

So basically the default value is only working when you convert from the external database but not when you save into the external db. 

To be honest I only read stuff from external db and I don't have a MySql already installed to do a quick test.

Hi "Box",

can you check that you have the same behaviour in your application (and not just the Aggregate previewer)?

According to documentation (and common sense) it should convert non-mandatory columns filled with NULL to the default value for the attribute (in your case -999)... If it is not, then I can see three possibilities:

  • You may not have published your extension after defining the default value to -999 or you may have forgotten to refresh the extension dependency on the module that is using it.
  • If the application shows the correct value (-999), but the Aggregate previewer shows the wrong value (zero, 0), then it's likely a bug in the Aggregate previewer that is converting to the platform's default value for the data type (which is 0) instead of the one you defined;
  • If both the application and the Aggregate previewer show the wrong value (zero, 0), then it's likely a bug in the generated extension code.

Thank you Sir,

I will retry it.


I have tried:

The result when i click the entity at design time is different from when i debug at run time; the first one result 0 (null) , and the later result as expected (-99999):