I'm trying do concat on some columns using WHEN condition on Azure Synapse Serverless, but there is a problem that in this new column it shows me every time only one column and the concat function doesn't work.

Here is the code:

SELECT 
    Categorie, ParentGuid,
    COALESCE(CAST(EnfantGuid_7 AS nvarchar(1000)),
             CAST(EnfantGuid_6 AS nvarchar(1000)), 
             CAST(EnfantGuid_5 AS nvarchar(1000)), 
             CAST(EnfantGuid_4 AS nvarchar(1000)), 
             CAST(EnfantGuid_3 AS nvarchar(1000)), 
             CAST(EnfantGuid_2 AS nvarchar(1000)),
             CAST(EnfantGuid_1 AS nvarchar(1000))) EnfantGuid,
    CASE 
        WHEN EnfantGuid_7 IS NOT NULL 
            THEN CONCAT_WS(', ', CAST(EnfantGuid_1 AS nvarchar(1000)), CAST(EnfantGuid_2 AS nvarchar(1000)), CAST(EnfantGuid_3 AS nvarchar(1000)), CAST(EnfantGuid_4 AS nvarchar(1000)), CAST(EnfantGuid_5 AS nvarchar(1000)), CAST(EnfantGuid_6 AS nvarchar(1000)))
        WHEN EnfantGuid_6 IS NOT NULL 
            THEN CONCAT_WS(', ', EnfantGuid_1, EnfantGuid_2, EnfantGuid_3, EnfantGuid_4, EnfantGuid_5)
        WHEN EnfantGuid_5 IS NOT NULL 
            THEN CONCAT_WS(', ',EnfantGuid_1, EnfantGuid_2, EnfantGuid_3, EnfantGuid_4)
        WHEN EnfantGuid_4 IS NOT NULL 
            THEN CONCAT_WS(', ',EnfantGuid_1, EnfantGuid_2, EnfantGuid_3)
        WHEN EnfantGuid_3 IS NOT NULL 
            THEN CONCAT_WS(', ', CAST(EnfantGuid_2 AS nvarchar(1000)), CAST(EnfantGuid_1 AS nvarchar(1000)))
        ELSE EnfantGuid_1
    END AS [Path],  
    EnfantGuid_1, EnfantGuid_2, EnfantGuid_3

All columns inside the CASE WHEN condition are of type UniqueIdentifier . I tried to cast them to string as shown below but no result..

Anyone have an idea for this problem please?

Sample of result:
| Category | ParentGuid | EnfantGuid | Path | EnfantGuid_1 | EnfantGuid_2 | EnfantGuid_3 | EnfantGuid_4 | EnfantGuid_5 | EnfantGuid_6 | EnfantGuid_7 |
| ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ | ------------ |
| a | 432025b5-5a5b | 36d9d9b3-5a5b | c4cae4b5-5a5b | c4cae4b5-5a5b | 66d9d9b3-5a5b | 36d9d9b3-5a5b | NULL | NULL | NULL | NULL | NULL |

In this row Path must contain EnfantGuid_1 + EnfantGuid_2 but it have only Enfant_Guid1 ==> The last CASE WHEN condition