docs: describes variable formatting options

csv option in postgres/mysql docs and the regex option in the
graphite docs

docs/sources/features/datasources/mysql.md

@@ -200,6 +200,14 @@ WHERE $__timeFilter(atimestamp) and hostname in([[hostname]])
 ORDER BY atimestamp ASC
 ```
 
+#### Disabling Quoting for Multi-value Variables
+
+Grafana automatically creates a quoted, comma-separated string for multi-value variables. For example: if `server01` and `server02` are selected then it will be formatted as: `'server01', 'server02'. Do disable quoting, use the csv formatting option for variables:
+
+`${servers:csv}`
+
+Read more about variable formatting options in the [Variables]({{< relref "reference/templating.md#advanced-formatting-options" >}}) documentation.
+
 ## Annotations
 
 [Annotations]({{< relref "reference/annotations.md" >}}) allows you to overlay rich event information on top of graphs. You add annotation queries via the Dashboard menu / Annotations view.
@@ -242,4 +250,4 @@ datasources:
     database: grafana
     user: grafana
     password: password
-```
+```