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Discover the fastest way to sort mixed `nvarchar` data numerically in SQL Server and resolve sorting challenges efficiently.
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Sorting nvarchar Column as Integer: A Quick Guide

Sorting data can often be a daunting task, especially when dealing with mixed data types in a single column. If you’re working with an nvarchar column that contains both textual and numeric values, you might find yourself stuck trying to sort the data in a numeric order. This guide addresses the common challenge of sorting a mixed nvarchar column in SQL Server by providing a practical solution that helps you achieve the desired order.

The Problem

When you have a column defined as nvarchar, sorting can yield unexpected results. For example, here’s a sample output you might encounter:

1

2

3

...

10

11

...

aaaa

aaab

b

ba

In the above list, the numeric values do not sort in the logical order you might expect. Instead, they curl into a lexicographical sort due to the nature of nvarchar data types, where string representations are compared character by character.

The Solution

To sort a mixed nvarchar column numerically, you can utilize SQL Server's ORDER BY clause alongside the ISNUMERIC function. Here’s the suggested SQL query:

[[See Video to Reveal this Text or Code Snippet]]

Let’s break down how this works:

Step 1: Determine Numeric vs. Non-Numeric Values

The first CASE statement differentiates between numeric and non-numeric values. By assigning a sorting priority (0 for numbers and 1 for non-numbers), we ensure that all numeric values are sorted first.

Step 2: Convert Numeric Values to Integer

The second CASE statement converts the numeric values to integers using CAST(column AS INT). This way, numeric values get sorted in their true numerical order rather than lexically.

Step 3: Sort Non-Numeric Values

Finally, the last part of the ORDER BY clause sorts the remaining non-numeric values using their default lexicographic order.

Important Notes

While the solution provided above will yield the expected results in terms of sorting, it's crucial to understand its performance implications:

Execution Plan: Using this query may result in a table-scan, which can be slow, particularly on large datasets. It creates temporary results that could potentially affect performance.

Testing: Always evaluate how the execution behaves with your specific dataset to ensure it meets your speed requirements.

Conclusion

Sorting an nvarchar column containing mixed data types requires thoughtful consideration of how SQL Server handles both numeric and non-numeric data. By following the structured method outlined above, you can effectively sort your data in numeric order while keeping performance in mind.

Whether you’re a seasoned SQL developer or just starting your journey with SQL Server, mastering data types and their behavior will greatly enhance your data manipulation skills. Implement this sorting technique today to ensure your data is organized precisely how you need it.