What to do if conversion failed when converting from a character string to uniqueidentifier?

1.6K Asked by Aalapprabhakaran in SQL Server , Asked on Sep 29, 2022

I am creating a Dynamic CRM 2011 Report in SSRS. I use several joins, And use GUID in joins. For ex Quote.OpportunityId=Opprtunity.OpportunityId

The problem comes from parameters. I have a parameter whose label is a name and the value is GUID of a record. I retrieve them from a Dataset. The query of the this Dataset(named siteDataset) is this :

select site.SiteId, site.Name from Site;

the siteId goes to the value of the parameter and site.name goes to the label of the parameter, the Parameter is named siteId itself.

But when I try to do this in another DataSet :

siteGUIDInAnotherEntity='@siteId'
Give me the subject Error. I even tried this :
CONVERT(VARCHAR(50), site.SiteId)
in siteId DataSet; But no success.

Answered by Ranjana Admin

If conversion failed when converting from a character string to uniqueidentifier - you shouldn't have those single quotes around @siteId, it should be like this:

siteGUIDInAnotherEntity=@siteId

The text string '@siteId' can't be converted into a uniqueidentifier for that join, and will result in the error you mentioned:

SELECT CAST('@siteId' AS uniqueidentifier);

Msg 8169, Level 16, State 2, Line 1

Conversion failed when converting from a character string to uniqueidentifier.

Your Answer

Answer (1)

Ranjana

If you encounter an error when trying to convert a character string to a uniqueidentifier in SQL Server, it typically means that the string does not conform to the format expected for a uniqueidentifier (i.e., a valid UUID/GUID format). Here are some steps to troubleshoot and resolve this issue:

1. Validate the Format of the String

Ensure that the string you are trying to convert matches the standard GUID format. A GUID should be in one of the following formats:

xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)
xxxxxxxxxxxxxx-xxxx-xxxx-xxxxxxxxxx (no hyphens)

Example of a valid GUID: 123e4567-e89b-12d3-a456-426614174000

2. Check for Leading/Trailing Spaces

  Trim any leading or trailing spaces from the string. Use the TRIM function to remove spaces.DECLARE @string NVARCHAR(50) = ' 123e4567-e89b-12d3-a456-426614174000 'SELECT CONVERT(uniqueidentifier, TRIM(@string))

3. Ensure Correct Data Type

Make sure the column or variable you are converting from is of type VARCHAR or CHAR and not of a type that might cause implicit conversion issues.

4. Use TRY_CONVERT or TRY_CAST

If you are working with potentially invalid data and want to handle errors gracefully, you can use TRY_CONVERT or TRY_CAST. These functions return NULL when the conversion fails instead of throwing an error.

  DECLARE @string NVARCHAR(50) = 'invalid-guid'SELECT TRY_CONVERT(uniqueidentifier, @string)

5. Validate Input Data

If you are getting data from an external source (e.g., a user input or a file), ensure the data is validated before attempting the conversion. You can use a regular expression to check if the string is a valid GUID.

6. Example of Handling Invalid GUIDs

Here's an example where you might handle invalid GUIDs in a table update:

  UPDATE YourTableSET YourGuidColumn =     CASE         WHEN TRY_CONVERT(uniqueidentifier, YourStringColumn) IS NOT NULL         THEN TRY_CONVERT(uniqueidentifier, YourStringColumn)         ELSE '00000000-0000-0000-0000-000000000000' -- or some default value    ENDWHERE SomeConditionExample to Identify Invalid GUIDsYou can identify and log invalid GUIDs using the following approach:

  SELECT YourStringColumnFROM YourTableWHERE TRY_CONVERT(uniqueidentifier, YourStringColumn) IS NULL

This will help you find any strings that are not valid GUIDs and take appropriate action.

By following these steps, you can troubleshoot and resolve issues related to converting character strings to uniqueidentifier in SQL Server.

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