Question

I have a column with a text data type , but its an xml field.When i try to execute a simple statement like

SELECT columnname,
       CONVERT(xml,coloumnname) 
  FROM employee

This is running fine in QA since it has small amount to data. When i am running in the prod then the exception shoots up. Is there a way so that it can bypasses all the records which has an illegal xml character so that i can execute the code successfully. Using sql sever 2005/2008.

do anyone have a scrip for this?

Answer 1

Validate data on-the-fly is slow enough.

1. If you really do not want to use bad data, you should add column to table (e.g. “Is_Validated”).

2. Then run script which will check data and if it is converted to xml without exception, update column as 1 else 0.

3. When you run your statement, you should limit converting to xml where Is_Validated=1 only.

4. When you insert new row, check if is valid XML (using TRY/CATCH logic or CLR) and insert only valid rows.

5. When you logic be stable you can begin to validate your bad data.

Update:

Because of script from #2 should be run only one time, it can be simple TSQL:
Assuming you have primary key Id as int and xml column Columnname in Table Employee validated by MySchema

 Declare @id int=0,@xml XML(MySchema)
WHILE EXISTS(SELECT * FROM Employee WHERE Id>@Id)
BEGIN
     SELECT TOP 1 @Id=Id FROM Employee WHERE Id>@Id ORDER BY Id
BEGIN TRY
  SET @xml=(SELECT columnname FROM Employee WHERE id=@Id)
      UPDATE Employee SET Is_Validated=1 WHERE Id=@Id
END TRY
    BEGIN CATCH
        UPDATE Employee SET Is_Validated=0 WHERE Id=@Id
    END CATCH
    END