Sql Server silently truncates varchar's in stored procedures

Decoding Silent Truncation

Silent truncation can lead to data integrity issues; however, context matters here:

• LEN vs DATALENGTH: While LEN skips trailing spaces during count, DATALENGTH includes them, like an obedient child.
• Parameters and limits: Be sure to validate parameters in the application before sending them on a trip to the database.
• varchar(max) and its consequences: Use varchar(max) judiciously to avoid performance issues. Always remember, with great power comes great responsibility!

Countermeasures

Here's how you deal with silent truncation issues:

• Validate lengths: Check the length of strings before they are sent to the stored procedure.
• Lengths of parameters: Craft stored procedures using parameters that align with table column lengths.
• Error handling in T-SQL: Make use of TRY/CATCH blocks to handle errors gracefully.
• Preventive checks at the application level: Employ the application level validation to ensure data integrity even before the data hits the database.

Best Practices for Avoiding Truncation

Let's explore some tactics to ensure data doesn't get lopped off unexpectedly:

1. Align Input with Its Container Sizes

For every use of varchar, ensure the following:

• Table column, variable lengths, and parameters are consistent with each other.
• Application-side validation prevents data input that might exceed column size limit.

2. Be Stringent About Settings

Implement stringent settings:

• Set ANSI_WARNINGS to ON across your SQL Server environment.
• Leverage the strict settings divulged in great detail by SQL experts, such as Erland Sommarkog.

3. Improve Error Handling

Ensure robustness in your procedures:

• Use Try/Catch, Try Again: Leverage TRY/CATCH blocks to capture and handle errors effectively.
• Transactions for life: Use transactions to ensure atomicity of operations and to prevent partial data commits.

Digging Deeper

Maintaining Mindfulness About Trailing Whitespace

Trailing spaces are sneaky, always account for them:

• LEN and DATALENGTH functions help you gauge the true length of your data.
• Keep in mind that LEN might ignore spaces at the end of a string, leading you to believe your data is shorter than it actually is. Tricky indeed!

Trap Errors With Table Variables

To effectively debug and catch errors:

• Use table variables as temporary containers for your data.
• Insert data into these tables and wait for the fireworks. Any failure can be a signal of potential issues with length limitations.

Take Cues from the Community

Absorb community insights:

• Incorporate feedback and suggestions offered by the SQL fraternity across various forums.
• Frequently update and audit your code to stay relevant with changing best practices.