Just quick to summarize the puzzle. Here is the quick recap of the same.
Now let us run following script.
DECLARE @FirstString VARCHAR(MAX)
DECLARE @SecondString VARCHAR(MAX)
DECLARE @ThirdString VARCHAR(MAX)
SET @FirstString = REPLICATE('A',4000)
SELECT LEN(@FirstString) LenFirstString;
SET @SecondString = REPLICATE('B',8000)
SELECT LEN(@SecondString) LenSecondString;
SET @ThirdString = REPLICATE('C',11000)
SELECT LEN(@ThirdString) LenThirdString;
The script above will return following result:
Quiz 1:
Pay attention to the last resultant and you will notice that the length of the @ThirdString is only 8000. WHY?
Answer 1:
The reason for the same is that if the first parameter of the REPLICATE function is not of type varchar(max) or nvarchar(max), REPLICATE truncates the return value at 8,000 bytes. To return values greater than 8,000 bytes, the first parameter must be explicitly cast to the appropriate varchar(max) or nvarchar(max).
Quiz 2:
What changes I should do in the REPLICATE function so it will give the appropriate result in the case of @ThirdString. In our case, it should return the value of 11000 and not 8000.
Answer 2:
To return the result as 11000, one has to just CAST or CONVERT the first parameters to VARCHAR(MAX) or NVARCHAR(MAX). Here is the example of the same.
DECLARE @ThirdString VARCHAR(MAX)
SET @ThirdString = REPLICATE(CONVERT(VARCHAR(MAX),'C'),11000)
SELECT LEN(@ThirdString) LenThirdString;
Now let us see the result set.
DB Optimizer
One last thing: Do not forget to download DB Optimizer XE3.5 Pro. It is my favorite tool for performance tuning.
If you notice that this was not very difficult puzzle but it was interesting for sure. There are so many valid answers that it will be not possible to name every single person. I strongly encourage all of you to go over the original blog post and read all the comments. Though all the comments are very similar there are so many new information there that I will say wealth of information just right there in the comments area.