"An Item with the Same Key Has Already Been Added" Error on Ssrs When Trying to Set Dataset

In SSRS, why do I get the error item with same key has already been added , when I'm making a new report?

It appears that SSRS has an issue(at leastin version 2008) - I'm studying this website that explains it

Where it says if you have two columns(from 2 diff. tables) with the same name, then it'll cause that problem.

From source:

SELECT a.Field1, a.Field2, a.Field3, b.Field1, b.field99 FROM TableA a
JOIN TableB b on a.Field1 = b.Field1

SQL handled it just fine, since I had prefixed each with an alias
(table) name. But SSRS uses only the column name as the key, not table
+ column, so it was choking.

The fix was easy, either rename the second column, i.e. b.Field1 AS
Field01 or just omit the field all together, which is what I did.

What is causing 'an item with the same key has already been added' error in ssrs?

The errors is because you have two columns with the same name :

oe_hdr.order_date,
po_hdr.order_date, 

You need to alias one of them

Same with

po_line.po_no,
oe_hdr.po_no,

Please ensure you format your code well so makes it easier to read

Easiest way to find them is to copy and paste your code into Notepad++ and double click on each column name.. notepad will highlight all instances of that word within the same document..

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

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!

SSRS: Getting An item with the same key has already been added

As @Jacob said, you have multiple fields with the same name: [Effective Date], [Board Cert (Y/N)]. While SSMS can handle this if you run the query, SSRS must have uniquely named columns so it knows what to put into each field of the report. One thing I started doing is putting the alias first, so instead of

dbr_addr.db_record_id AS db_record_id_addr

I would put

db_record_id_addr = dbr_addr.db_record_id 

That nicely lines up all of the column names so they're easy to see.

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

You do indeed have two columns with the same name. Your expression aliased rnum and #PostCardAppointmentBack.rnum. Either rename one of these, or avoid using the * shortcut and specify your columns explicitly.

Getting error: An item with the same key has already been added - error/warning in SSRS report

You have 2 columns with the same exact name Total Direct Activites HH:MM. SSRS cannot deal with that. Change one, then this should work.

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