Check Constraint : col1 Null if col2 Not Null

Answers

• Alex B Redgate › Posts: 1,158 Diamond 4

  March 26, 2019 6:42PM

  Hi @RomainH,
  
  You can return DBNull like this to return NULL
  

  return DBNull

  
  But I couldn't get a check for a row value of NULL to work.  I tried
  

  val is None
  val is not None
  val is DBNull
  val is DBNull.Value
  val == DBNull
  val == DBNull.Value

  But couldn't get it to work.
  
  If I did 
  

  def main(config):
          if (col2 == "notnull   "):
          return 4
      else:
          return DBNull
      return 0<br>

  Then it would correctly place null or the number 4
  ​
  
  But that required me to know the value of col2 to check against.
  
  So I'm not sure what might work here, perhaps you have solved that part of it and just returning DBNull will get you there, if so please let us know!
  
  Kind regards,
  Alex

  Product Support Engineer | Redgate Software
  
  Have you visited our Help Center?

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• pdb Posts: 1 New member

  January 12, 2023 9:47AM edited January 12, 2023 10:29AM

  Alex B said:

  
  But I couldn't get a check for a row value of NULL to work.  I tried
  

  val is None
  val is not None
  val is DBNull
  val is DBNull.Value
  val == DBNull
  val == DBNull.Value

  But couldn't get it to work.
  

  
  Hello, I am struggeling with the same issue. Are there any updates on "how to check another column value for null within a python script"?
  
  EDIT: Finally found out myself. We need to use

  val.IsNull

  Found it by accident. Where is a documentation for that?

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