Exploring Limitations and Alternatives between SQL Server and Azure Synapse Analytics

When migrating from SQL Server to Azure Synapse Analytics, it’s essential to understand the differences and limitations between the two platforms. In this article, we will explore specific limitations in Synapse Analytics compared to SQL Server and discuss alternative approaches to overcome these limitations.

 

1.In Azure Synapse Analytics, the cross-database queries / linked servers are not supported. This means you cannot directly select data from one database to another within the same Azure Synapse Analytics instance.

 

SQL Server:

SELECT *
FROM DbName.SchemaName.TableName1 AS T1
JOIN DbName.SchemaName.TableName2 AS T2 ON T1.ID = T2.ID;

Alternative:

As an alternative, you can leverage ETL tools like Microsoft SSIS and Azure Data Factory to export data from one database and import it into another.

 

 

2.In Synapse Analytics, using the OFFSET/FETCH clause to retrieve a subset of rows is not supported. Instead, you can use alternative approaches such as using the ROW_NUMBER() function combined with a subquery or using a CTE with filtering conditions.

SQL Server:

SELECT * 
FROM TableName 
ORDER BY Id
OFFSET 2 ROWS 
FETCH NEXT 2 ROWS ONLY;

 

Azure Synapse Analytics – Alternative:

SELECT *
FROM
(
    SELECT *, ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum
    FROM TableName
) AS Subquery
WHERE RowNum BETWEEN 3 AND 4;

 

3.The FOR XML clause, used for generating XML output from query results, is not supported in Synapse Analytics. As an alternative, you can consider processing the query using other external tools to transform the result set into XML format.

 

SQL Server:

SELECT ColumnName1, ColumnName2 FROM Table FOR XML AUTO;

 

Alternative:

Process the query results programmatically or use external tools to generate XML output from the result set.

 

4.The IIF function is not supported in Azure Synapse Analytics.

 

SQL Server:

SELECT ColumnName1,
       ColumnName2,
       IIF(Condition, Value1, Value2) AS Result
FROM TableName;

 

Azure Synapse Analytics – Alternative:

SELECT ColumnName1,
       ColumnName2,
       CASE
           WHEN Condition THEN Value1
           ELSE Value2
       END AS Result
FROM TableName;

 

While Azure Synapse Analytics offers a powerful analytics platform, it does have certain limitations compared to SQL Server. By understanding these limitations and exploring alternative approaches, you can effectively migrate and optimize your data workloads in Synapse Analytics.