“An item with the same key has already been added” Error on SSRS When Trying to Set Dataset

Question

When i try to set the Dataset in SSRS IDE, i get the error you see in the snapshot.

The query works totally fine in SQL Server Management Studio, i wonder where did

Answer 1

I came across this post today when I received the same issue. My problem how-ever was a little bit different.

I had a temporary table and an If statement in my SP. So my SP looked something like this:

DECLARE @myCheck as int
SET @myCheck = 0

SELECT @myCheck = CASE WHEN [checkfield] = 'xxx' then 1 else 0 end
  FROM  checktable
  WHERE ...


SELECT myfields.*
into #temptable
FROM mytable
WHERE ...


IF @myCheck = 1     --if ssrs does'nt want ot refresh your fields, remove hte if as it does not see past this...
    select *
    FROM #temptable
        LEFT JOIN tableA
            ON ...
ELSE
    select *
    FROM #temptable
        LEFT JOIN tableB
            ON ...

So in order to "refresh" my fields in SSRS, I commented out the If statement and kept one of my queries with the field names. Just had to remember to add everything back afterwards...

Using Visual Studio 2012 / SQL 2012

Answer 2

After formatting your script a bit, I noticed that there are 2 columns with the same name that you are selecting. Make sure to change the final name & that every column when you do run your statement in Management Studio has a unique name.

That being said, the two columns I noticed have duplicate names are customerquoteproducts.istaxpaid and customershipping.istaxpaid

I hope that helps!