# COLLECT\$1SET function
<a name="COLLECT_SET"></a>

The COLLECT\$1SET function collects and returns a set of unique elements. 

This function is useful when you want to collect all the distinct values from a set of rows into a single data structure, without including any duplicates.

**Note**  
The function is non-deterministic because the order of the collected results depends on the order of the rows, which may be non-deterministic after a shuffle operation is performed.

## Syntax
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```
collect_set(expr)
```

## Arguments
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 *expr*   
An expression of any type except MAP.

## Returns
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Returns an ARRAY of the argument type. The order of elements in the array is non-deterministic. 

NULL values are excluded.

## Example
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The following query collects all the unique values from the col column into a set. The `VALUES` clause is used to create an inline table with three rows, where each row has a single column col with the values 1, 2, and 1 respectively. The `collect_set()` function is then used to aggregate all the unique values from the col column into a single set. The output of this SQL statement would be the set `[1,2]`, which contains the unique values from the col column. The duplicate value of 1 is only included once in the result.

```
SELECT collect_set(col) FROM VALUES (1), (2), (1) AS tab(col);
 [1,2]
```