A CONCAT Function For The Rest Of Us

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A CONCAT Function For The Rest Of Us

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mike.mcquillan

Posted Friday, May 18, 2012 1:14 PM

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Comments posted to this topic are about the item A CONCAT Function For The Rest Of Us

Post #1302784

steve.ledridge

Posted Monday, May 21, 2012 12:29 PM

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Why would I use this function rather than simply joining the strings with "+" as it does inside the function. Especially when there are more that two strings being joined, where it looks like it would be more expensive to call a function multiple times.

Post #1303595

mike.mcquillan

Posted Monday, May 21, 2012 3:42 PM

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Hi Steve

Nobody is making you use the function. But to give one quick example where it could be useful. Say you have two string variables, and one of them is NULL. If you simply use + to add these together, you'll receive NULL - i.e. the valid string value will be lost. Using this CONCAT function, the string will be returned.

Example:

DECLARE @S1 VARCHAR(10)
DECLARE @S2 VARCHAR(10) = 'Hello'

SELECT dbo.CONCAT(@S1, @S2, 1) -- Returns 'Hello'

Regards,
Mike.

Post #1303773

steve.ledridge

Posted Monday, May 21, 2012 3:56 PM

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I didn't mean to imply that I was being forced. I was just trying to see if I was missing an aspect that would make it more useful in some places. But what it seems like is that there is no benefit over the tried and true method that most of us have been using for years with either coalesce or isnull.

select COALESCE(@String1,'') + ISNULL(@String2,'')

Post #1303776

steve.ledridge

Posted Monday, May 21, 2012 4:09 PM

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OK, I have found a benefit of the CONCAT function in SQL 2012. it is automatically converting data types to strings and outputting them rather than giving you data type mismatches, and forcing you to convert all the inputs. I can also see how people will consider this lazy and at least in the case of DateTime fields, you would generally convert to a specific format.

but instead of coding :
SELECT 'Current Time ' + CAST(GETDATE() AS VARCHAR(20))
you could use
SELECT CONCAT('Current Time ', GETDATE())

Post #1303778

daryl.scott

Posted Wednesday, June 06, 2012 7:19 AM

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The SQL Server 2012 CONCAT function accepts two or more string values. The user-defined CONCAT function accepts only two values. It's the "two or more" part that would be valuable.

Post #1311850

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