Trim is one of the most frequently used operation over String data types. A developer often come across a scenario where they have the string with leading and trailing spaces around string. If your business logic suggests that the logs around the spaces are not useful they should be trimmed. However, in SQL Server there is no TRIM function. When a TRIM function is used it will throw an error.
For example, here is the script when executed it will throw an error.
-- The following will throw an error DECLARE @String1 NVARCHAR(MAX) SET @String1 = ' String ' SELECT TRIM(@String1) TrimmedValue GO
The above script will return following error:
Msg 195, Level 15, State 10, Line 4
‘TRIM’ is not a recognized built-in function name.
Let us not everything why this simple function is not implemented but try to resolve how we can achieve the result of the same function. SQL Server has two functions which when nested can give us the same result as a TRIM function.
1) RTRIM – Removes the Spaces on the right side (or leading spaces) of the string
2) LTRIM – Removes the Spaces on the left side (or trailing spaces) of the string
We can combine them as following and it will not throw an error.
-- The following will work
DECLARE @String1 NVARCHAR(MAX)
SET @String1 = ' String '
SELECT @String1 OriginalString, RTRIM(LTRIM(@String1)) TrimmedValue
Let us see the same concept in following SQL in Sixty Seconds Video:
Additionally, if you want you can create a user defined function which is using RTRIM and LTRIM and can use the function when trim functionality is required.
-- Create Function
CREATE FUNCTION dbo.TRIM(@string VARCHAR(MAX))
SELECT dbo.TRIM(' String ')
Now when we are on the topic of the TRIM function, let me remind you one very important impact of this function if used in the WHERE clause. If any function is used in the WHERE clause, it will negatively impact on the performance of the query. SQL Server has to process the function on whole column leading Table Scan or Index Scan instead of Index Seek. This will increase the resource utilization and lead to poor performance. However, using this function in SELECT statement does not degrade performance much. In simple words – please be mindful of using any functions. Use the functions when you absolutely need it or enforcing business needs.
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What would you like to see in the next SQL in Sixty Seconds video?
Reference: Pinal Dave (http://blog.sqlauthority.com)