# IsUnknown

{% hint style="info" %}
The **`IsUnknown()`** function checks whether the input parameter is unknown and not recognizable as a value or element. 

It is only <mark style="color:orange;">slightly different</mark> from[ `IsEmpty()` ](/platform/wemreference/functions/validation/isempty.md)in the way that an empty text-value is a known element (it is a text and not unknown),  but it does not have a value.&#x20;

This function is SQL compatible. For more information about SQL compatibility, see our [documentation](/platform/wemreference/sql-compatibility.md).
{% endhint %}

{% hint style="danger" %}
**We advise to use the** [**HasValue()**](/platform/wemreference/functions/validation/hasvalue.md) **and** [**IsEmpty()**](/platform/wemreference/functions/validation/isempty.md) **functions as they are more practical and logical in use.**
{% endhint %}

{% hint style="warning" %}
If the input parameter is a list or a collection (like a Concept-Set), then the `IsUnknown()` function checks if the list has no rows.

The [`IsKnown()`](/platform/wemreference/functions/validation/isknown.md) function checks the opposite of this function.
{% endhint %}

{% hint style="success" %}
Returns <mark style="color:green;">`true`</mark> if <mark style="color:blue;">`parameter`</mark> is unknown.\
Returns <mark style="color:red;">`false`</mark> if <mark style="color:blue;">`parameter`</mark> is not unknown.&#x20;
{% endhint %}

### Syntax

<details>

<summary><code>IsUnknown(</code><mark style="color:blue;"><code>parameter</code></mark><code>)</code></summary>

`IsUnknown( "1" )`\
\&#xNAN;*=> False*

`IsUnknown(`*`unknownnumber`*`)`\
\&#xNAN;*=> True*

`IsUnknown( "" )`\
\&#xNAN;*=> False >> <mark style="color:orange;">This is different from IsEmpty( "" ) : "" is a known element (an empty string) but it does not have a value according to the IsEmpty implementation</mark>.*

`IsUnknown( "` `" )`\
\&#xNAN;*=> False*

`IsUnknown( '' )`\
\&#xNAN;*=> False*

`IsUnknown( {} )`\
\&#xNAN;*=> True*

`IsUnknown( [List WithRows] )`\
\&#xNAN;*=> False*

`IsUnknown( [List WithNoRows] )`\
\&#xNAN;*=> True*

`IsUnknown(ToString(`*`unknownstring`*`))`\
\&#xNAN;*=> **FALSE** > <mark style="color:orange;">the ToString on UnknownString makes the element Known as a String Type but with an Empty Value >> better use the HasValue or IsEmpty functions for more practical and logical use</mark>*

</details>

### Parameters

<table><thead><tr><th width="150">Name</th><th width="150">Type</th><th width="150" align="center">Required</th><th width="284.6178790534619">Description</th><th data-hidden>Required?</th></tr></thead><tbody><tr><td><mark style="color:blue;">parameter</mark></td><td>any</td><td align="center"><span data-gb-custom-inline data-tag="emoji" data-code="2611">☑️</span></td><td>Field that is checked for a value </td><td>yes</td></tr></tbody></table>


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