When working with SQL Server, you may come across situations where you need to handle really long strings, exceeding the default limit of 8000 characters. One common scenario where this occurs is when dealing with dynamic SQL. However, it’s important to be aware of the limitations and potential mistakes that can arise when working with long strings.

By default, SQL Server treats strings as varchar data type. This is evident from the result of the following query:

SELECT SQL_VARIANT_PROPERTY('A string','BaseType');
-- Returns: varchar

It’s worth noting that the varchar data type has a limit of 8000 characters, while varchar(max) can store up to 2GB of data. This distinction is crucial when dealing with long strings.

Let’s consider an example to illustrate a common mistake that can occur when working with long strings:

DECLARE @str varchar(max);
SET @str = REPLICATE('1',950) +
REPLICATE('2',950) +
REPLICATE('3',950) +
REPLICATE('4',950) +
REPLICATE('5',950) +
REPLICATE('6',950) +
REPLICATE('7',950) +
REPLICATE('8',950) +
REPLICATE('9',950) +
REPLICATE('0',950); 
SELECT LEN(@str);
-- Output: 8000

In this example, we are attempting to create a string with a length of 9500 characters. However, due to the limitation of the varchar data type, the resulting string is truncated to 8000 characters. This can lead to unexpected behavior and errors, especially when working with dynamic SQL.

To overcome this limitation, it is recommended to break up long strings into smaller chunks:

DECLARE @str varchar(max);
SET @str = REPLICATE('1',950) +
REPLICATE('2',950) +
REPLICATE('3',950) +
REPLICATE('4',950) +
REPLICATE('5',950); 
SET @str = @str + 
REPLICATE('6',950) +
REPLICATE('7',950) +
REPLICATE('8',950) +
REPLICATE('9',950) +
REPLICATE('0',950); 
SELECT LEN(@str);
-- Output: 9500

By breaking up the string into smaller chunks, we ensure that the final string length is preserved and does not exceed the limit.

It’s important to be cautious when working with long strings in SQL Server. While breaking up the strings is a good practice, it’s always recommended to plan and design your queries in a way that avoids reaching the length limits. This can help prevent potential issues and ensure the integrity of your data.

Next time you encounter a strange error that seems to indicate string truncation, remember to check the length of your string and consider the limitations of the varchar data type.

Happy coding!