Docs: Update labels to fields transform (#30086)

* Docs: Update labels to fields transform

* Update docs/sources/panels/transformations/types-options.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/panels/transformations/types-options.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Moved merge info to before examples

* Update docs/sources/panels/transformations/types-options.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* More review updates

* Update docs/sources/panels/transformations/types-options.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

docs/sources/panels/transformations/types-options.md

@@ -188,14 +188,12 @@ In the example below, I added two fields together and named them Sum.
 
 ## Labels to fields
 
-> **Note:** In order to apply this transformation, your query needs to return labeled fields.
+This transformation changes time series results that include labels or tags into to a table structure where each label becomes its own field.
 
-When you select this transformation, Grafana automatically transforms all labeled data into fields.
+Given a query result of two time series:
 
-Example: Given a query result of two time series
-
-1: labels Server=Server A, Datacenter=EU
-2: labels Server=Server B, Datacenter=EU
+* Series 1: labels Server=Server A, Datacenter=EU
+* Series 2: labels Server=Server B, Datacenter=EU
 
 This would result in a table like this:
 
@@ -204,7 +202,7 @@ This would result in a table like this:
 | 2020-07-07 11:34:20 | Server A | EU         | 1     |
 | 2020-07-07 11:34:20 | Server B | EU         | 2     |
 
-**Value field name**
+### Value field name
 
 If you selected Server as the **Value field name**, then you would get one field for every value of the Server label.
 
@@ -212,13 +210,31 @@ If you selected Server as the **Value field name**, then you would get one field
 | ------------------- | ---------- | -------- | -------- |
 | 2020-07-07 11:34:20 | EU         | 1        | 2        |
 
-For this example, I manually defined labels in the Random Walk visualization of TestData DB.
+### Merging behavior
+
+The labels to fields transformer is internally two separate transformations. The first acts on single series and extracts labels to fields. The second is the [merge](#merge) transformation that joins all the results into a single table. The merge transformation tries to join on all matching fields. This merge step is required and cannot be turned off.
+
+To illustrate this, here is an example where you have two queries that return time series with no overlapping labels. 
+
+* Series 1: labels Server=ServerA
+* Series 2: labels Datacenter=EU
+
+This will first result in these two tables:
+
+| Time                | Server  | Value | 
+| ------------------- | ------- | ----- | 
+| 2020-07-07 11:34:20 | ServerA | 10
 
-{{< docs-imagebox img="/img/docs/transformations/labels-to-fields-before-7-0.png" class="docs-image--no-shadow" max-width= "1100px" >}}
+| Time                | Datacenter | Value | 
+| ------------------- | ---------- | ----- |
+| 2020-07-07 11:34:20 | EU         | 20
 
-After I apply the transformation, my labels appear in the table as fields.
+After merge: 
 
-{{< docs-imagebox img="/img/docs/transformations/labels-to-fields-after-7-0.png" class="docs-image--no-shadow" max-width= "1100px" >}}
+| Time                | Server  | Value | Datacenter |
+| ------------------- | ------- | ----- | ---------- |
+| 2020-07-07 11:34:20 | ServerA | 10    |            |
+| 2020-07-07 11:34:20 |         | 20    | EU         |
 
 ## Group by