Issue in fn!union() to return unique values. Is there any other function available?

if I understood your query correctly, you want to fetch distinct values from a list and remove null values.

In that case, you can use union using same list twice and pass the output in reject().

Something like:-

a!localVariables(
local!a : {1, 2, 2, 1, 3, 1, null, null },
reject(fn!isnull,union(local!a,local!a))
)

HI, If you want to use union() then you are expected to pass two arrays, from your requirement, your code should look something like below,

a!localVariables(
  local!input:{ 1, 2, 2, 1, 3, 1, null, null},
union(local!input, local!input),


)

Yes, Agree but normally its look Appain was failed in sometimes of execution right. Assume if user are passing same data twice but Appian needs to handle this also right it union() passed one parameter then it return outputs instead of error as invalid parameter

@appian

Hi,

you want to use union() then you need to pass two parameter. and also you want to remove null values form output, then code should look like below

a!localVariables(
  local!input1: { 1, 2, 2, 1, 3, 1, null, null},
  local!input2: { 1, 2, 2, 1, 3, 1, null, null},
  reject(a!isNullOrEmpty(_), union(local!input1, local!input2))
)

What does union mean? set of all unique elements from multiple sets. So, there should be more than one array to perform a union right? it is mentioned in the documentation on the Expression rule designer as well that atleast two arrays are required for union to work as expected although it can take n number of arrays. Consider this as sum of numbers which always require more than one number to execute.

Now, you can try what other contributors suggested (passing the same array as second parameter) or you can fool Appian by passing an empty list as a second parameter which would also yield the same result.

union({ 1, 2, 2, 1, 3, 1, null, null }, tointeger({}))

Unknown said:

its look Appain was failed in sometimes of execution right

This seems less like a case of "appian was failed" and more of a case of you not understanding the parameters of Appian's union() function, which requires 2 arrays as input.

This works perfectly.  You pass in an array with three 1's, two 2's, a 3, and 2 nulls, and pass in another array with a 9 in it.  Union does exactly what it says on the tin.  It joins the arrays and removes the duplicates.  You only have 1 null in the result set.  If you don't want it, reject(a!isNullOrEmpty(_), local!list).

Union doesn't say it does anything or doesn't do anything to nulls.  It says it removes duplicates, and it did.

The UNIQUE function in Excel returns a list of unique values from a range or array. It works with any data type: text, numbers, dates, times, etc.

The function is categorized under Dynamic Arrays functions. The result is a dynamic array that automatically spills into the neighboring cells vertically or horizontally.

The syntax of the Excel UNIQUE function is as follows:

UNIQUE(array, [by_col], [exactly_once])

Where:

Array (required) - the range or array from which to return unique values.

By_col (optional) - a logical value indicating how to compare data:

TRUE - compares data across columns.
FALSE or omitted (default) - compares data across rows.

Exactly_once (optional) - a logical value that defines what values are considered unique:

TRUE - returns values that occur only once, which is the database notion of unique.
FALSE or omitted (default) - returns all distinct (different) values in the range or array.

How does your post help the TO in Appian?