Is there a smarter way to pick unique records being fetched by a query expression?

Question

Hi All,

My name is Sam and i am new to Appian development and hence might be asking a few rudimentary questions. For this one, i have a query expression that is returning me a year value as {2019, 2019,2019,2018,2018,2017}. As you see this is returning values from different rows of a database. Now what i would like to do is get the unique values from this list so my output should like "{2019,2018,2017}". After studying the built in functions the only function i was able to use to achieve what i need was union () where my code looked like union((rule!<rule>(year)),rule!<rule>(year))) , where i am doing a union between the same set of data. Somehow i feel this is not efficient. Is there any other built in function that woudl allow me to extract the unique values from my array list with duplicates.

Any pointers would be helpful.

Thanks again community.

Reg,

Sam

ManuelHTG · Answer

Hi Sam, 
 
I would do a new expression rule to eliminate duplicates. 
 
The union is not a bad approach, however I would create a new expression rule that removes the duplicates. In general, you should try to minimize calls to the DB so supporting with an expression rule that has a "ri!" or using a load() variable would be better. 
 
Another way would be by doing loopings. In general, Appian does not work very well with arrays. For arrays I usually work with loops, as then you can work item by item and it is more transparent what you are doing. 
 
Probably this functions would be useful. 
 
wherecotains() docs.appian.com/.../fnc_array_wherecontains.html 
 
a!forEach() docs.appian.com/.../fnc_looping_a_foreach.html 
 
Anyways, an expression rule that eliminates duplicates is always useful. 
 
Good luck!

Is there a smarter way to pick unique records being fetched by a query expression?

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