How to Correctly Concatenate Numbers and Strings in T-SQL to Format Numbers?

How to Concatenate Numbers and Strings to Format Numbers in T-SQL

Scenario

You have created a function, ActualWeightDIMS, that concatenates integer values representing actual weight, length, width, and height to display as a formatted string. However, when calling the function with a SELECT statement, you receive an error indicating conversion failure when converting varchar 'x' to integer.

Issue

The error stems from the function's incorrect concatenation of integer parameters with strings. SQL Server interprets the addition of an integer (@Actual_Dims_Lenght) to a string ('x') as a mathematical operation, leading to a conversion error.

Solution

To resolve this issue, you need to explicitly convert your integer parameters to VARCHAR before concatenating them with strings. Here's how you should modify your function:

SET @ActualWeightDIMS =
     CAST(@Actual_Dims_Lenght AS VARCHAR(16)) + 'x' +
     CAST(@Actual_Dims_Width  AS VARCHAR(16)) + 'x' +
     CAST(@Actual_Dims_Height  AS VARCHAR(16))

By casting the integer parameters to VARCHAR, you ensure that the operation is treated as string concatenation, resulting in the desired formatted output.

Additional Considerations

You mentioned that users can only select either weight or dimensions on an ASP.net page. You asked if you need to handle this validation on the SQL side. While it is not strictly necessary, it can provide an additional layer of safety. You could add a CHECK constraint in the database to ensure that when the user selects dimensions, all three dimension values (length, width, and height) are non-NULL. This would prevent the function from returning incorrect or incomplete results.

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