I have a table that contains NULL values but the problem is that some of the values are actually string "NULL" and not actual NULLS so when you trying something like

where date is null

it will not return the fields that have the "NULL" string.

What I am needing to do is run an update of the whole table that will convert all string "NULLS" to the actual NULL value. The "NULL" strings happen throughout all columns of the table so it is not just 1 column that needs to be updated. I am not sure how to approach this scenario. I'm thinking I might need to use a loop since i have many columns but then again there might be a simple solution without having to use a loop. What would be the best way to resolve this issue?

  • Are we talking about 4-5 columns? Or about 100 columns? Apr 18, 2013 at 18:39
  • more like 30 to 40 columns
    – Juan Velez
    Apr 18, 2013 at 18:41

1 Answer 1


SET @sql = N'';

SELECT @sql = @sql + '
  ' + QUOTENAME(name) + ' = CASE
  WHEN ' + QUOTENAME(name) + ' = ''NULL'' THEN NULL ELSE '
  + QUOTENAME(name) + ' END,'
FROM sys.columns
WHERE [object_id] = OBJECT_ID('dbo.YourTableName')
AND system_type_id IN (35,99,167,175,231,239);

SELECT @sql = N'UPDATE dbo.YourTableName SET ' + LEFT(@sql, LEN(@sql)-1) + ';';

PRINT @sql;
--EXEC sp_executesql @sql;
  • @Aaron, where could we find the lookup table for the system_type_id? Thanks in advance.
    – Travis
    Apr 18, 2013 at 20:21
  • They're in sys.types Apr 18, 2013 at 20:22
  • @Aaron, maybe I am not in the right page. This is the MSDN page (msdn.microsoft.com/en-us/library/ms188021.aspx) I was looking at, but it doesn't have the list of system_type_id and its corresponding data type.
    – Travis
    Apr 18, 2013 at 20:24
  • @Travis the documentation does not list all of the values, it just describes the view itself. If you want to see the values, just run a select: SELECT * FROM sys.types; Apr 18, 2013 at 20:25
  • @Aaron. Never mind. It is in the sys.types table..
    – Travis
    Apr 18, 2013 at 20:25

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