Creating a Stored Procedure to Delete Records from Fact Tables Using a Parameterized Query

Dynamic Stored Procedure to Delete Records from Fact Tables

As a technical blogger, I’ve been approached by several developers who face a common challenge when dealing with deleted records in fact tables. The problem statement is as follows: a developer has a set of fact tables that contain deleted records and wants to run a stored procedure to eliminate these records from all fact tables. The twist is that the table names are dynamic, and the developer wants to use a lookup table IsDeletedRecords with IDs and a parameterized table name.

In this article, we’ll explore how to create a stored procedure that deletes all records using a lookup table ID and a parameterized table name. We’ll also delve into the details of the SQL statements used in the process and provide explanations for the code snippets.

The Challenge: Deleting Records from Fact Tables

When dealing with deleted records in fact tables, it’s essential to consider the relationships between these tables. Typically, fact tables are joined with dimension tables or lookup tables to retrieve relevant data. In this scenario, we’re working with a set of fact tables that contain deleted records and a table called IsDeletedRecords that only contains IDs of deleted records.

To delete records from all fact tables, we need a stored procedure that can dynamically generate the SQL statement for each fact table. This approach requires using parameterized queries to ensure that the SQL statement is secure and prevents SQL injection attacks.

The Initial Approach

The initial solution attempted by the developer uses the following code:

CREATE PROCEDURE [dbo].[DeleteTableRows]
    @TableName varchar (100)
AS
BEGIN
    DECLARE @schema VARCHAR(256) = 'tst'
    DECLARE @SqlText NVARCHAR(MAX)

    SET @SqlText = 'DELETE' + QUOTENAME(@TableName) +  
                   'FROM' + QUOTENAME(@TableName) + 
                   ' INNER JOIN [del].[IsDeleteIDs] b ON' + QUOTENAME(@TableName) + '.id = b.id'

    EXEC sp_executesql @SqlText
END

Although this approach looks reasonable, it has a few issues:

The INNER JOIN clause is incorrect. It should be ON instead of AND.
There’s no way to dynamically generate the SQL statement for each fact table.

The Correct Approach

The correct solution involves using a parameterized query with a SELECT statement to retrieve the IDs of deleted records from the IsDeletedRecords table. Here’s the corrected code:

CREATE PROCEDURE [dbo].[DeleteTableRows]
    @TableName varchar (100)
AS
BEGIN
    DECLARE @schema VARCHAR(256) = 'tst'
    DECLARE @SqlText NVARCHAR(MAX)

    SET @SqlText = 'DELETE FROM ' + QUOTENAME(@TableName) +  
                   ' WHERE id IN (SELECT id FROM [del].[IsDeleteIDs] WHERE TableName = '''' + @TableName + ''' )'

    EXEC sp_executesql @SqlText
END

This code uses a SELECT statement to retrieve the IDs of deleted records from the IsDeletedRecords table. The WHERE clause filters the results based on the TableName column.

Explanation and Example

Let’s break down the SQL statement used in this solution:

DELETE FROM [tst].[bookableresource]`: Deletes all records from the specified fact table.
WHERE id IN (SELECT id FROM [del].[IsDeleteIDs] WHERE TableName = '''' + @TableName + ''' ): Filters the results based on the IDs of deleted records.

The IN clause is used to filter the records that match the conditions. In this case, we’re using a subquery to retrieve the IDs of deleted records from the IsDeletedRecords table.

Best Practices and Security Considerations

When creating stored procedures like this one, it’s essential to consider security best practices:

Use parameterized queries: Always use parameterized queries to prevent SQL injection attacks.
Validate user input: Validate any user input or parameters to ensure they meet the required criteria.

Conclusion

In conclusion, deleting records from fact tables can be a challenging task, especially when dealing with dynamic table names. By using a stored procedure that generates a dynamic SQL statement based on the IsDeletedRecords lookup table, we can efficiently eliminate deleted records from all fact tables. Remember to follow best practices and security considerations when creating stored procedures like this one.

Additional Considerations

While the provided solution covers the basic requirement of deleting records from fact tables using a parameterized query, there are additional considerations:

Handling NULL values: If the IsDeletedRecords table contains NULL values for deleted record IDs, you’ll need to modify the SQL statement to handle this case.
Supporting multiple lookup tables: If you have multiple lookup tables with different names, you may want to consider using a more flexible approach, such as using a parameterized query or a dynamic SQL script.
Optimizing performance: Depending on the size of your fact tables and IsDeletedRecords table, optimizing performance may be essential. You can use indexing, caching, or other techniques to improve query performance.

By considering these additional factors, you can create an even more robust and efficient solution for deleting records from fact tables using a parameterized query.

Last modified on 2025-03-16