Docs: Add SQL region annotation examples (#23268)

Add region annotation examples for SQL data sources in docs.

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

docs/sources/features/datasources/mssql.md

@@ -381,7 +381,7 @@ Read more about variable formatting options in the [Variables]({{< relref "../..
 Name | Description
 ------------ | -------------
 time | The name of the date/time field. Could be a column with a native SQL date/time data type or epoch value.
-timeend | Optional name of the end date/time field. Could be a column with a native SQL date/time data type or epoch value.
+timeend | Optional name of the end date/time field. Could be a column with a native SQL date/time data type or epoch value. (Grafana v6.6+)
 text | Event description field.
 tags | Optional field name to use for event tags as a comma separated string.
 
@@ -411,6 +411,23 @@ WHERE
 ORDER BY 1
 ```
 
+**Example region query using time and timeend columns with epoch values:**
+
+> Only available in Grafana v6.6+.
+
+```sql
+SELECT
+  time_sec as time,
+  time_end_sec as timeend,
+  description as [text],
+  tags
+FROM
+  [events]
+WHERE
+  $__unixEpochFilter(time_sec)
+ORDER BY 1
+```
+
 **Example query using time column of native SQL date/time data type:**
 
 ```sql

docs/sources/features/datasources/mysql.md

@@ -350,6 +350,22 @@ WHERE
   $__unixEpochFilter(epoch_time)
 ```
 
+**Example region query using time and timeend columns with epoch values:**
+
+> Only available in Grafana v6.6+.
+
+```sql
+SELECT
+  epoch_time as time,
+  epoch_timeend as timeend,
+  metric1 as text,
+  CONCAT(tag1, ',', tag2) as tags
+FROM
+  public.test_data
+WHERE
+  $__unixEpochFilter(epoch_time)
+```
+
 **Example query using time column of native SQL date/time data type:**
 
 ```sql
@@ -366,7 +382,7 @@ WHERE
 Name | Description
 ------------ | -------------
 time | The name of the date/time field. Could be a column with a native SQL date/time data type or epoch value.
-timeend | Optional name of the end date/time field. Could be a column with a native SQL date/time data type or epoch value.
+timeend | Optional name of the end date/time field. Could be a column with a native SQL date/time data type or epoch value. (Grafana v6.6+)
 text | Event description field.
 tags | Optional field name to use for event tags as a comma separated string.
 

docs/sources/features/datasources/postgres.md

@@ -354,6 +354,22 @@ WHERE
   $__unixEpochFilter(epoch_time)
 ```
 
+**Example region query using time and timeend columns with epoch values:**
+
+> Only available in Grafana v6.6+.
+
+```sql
+SELECT
+  epoch_time as time,
+  epoch_time_end as timeend,
+  metric1 as text,
+  concat_ws(', ', metric1::text, metric2::text) as tags
+FROM
+  public.test_data
+WHERE
+  $__unixEpochFilter(epoch_time)
+```
+
 **Example query using time column of native SQL date/time data type:**
 
 ```sql
@@ -370,7 +386,7 @@ WHERE
 Name | Description
 ------------ | -------------
 time | The name of the date/time field. Could be a column with a native SQL date/time data type or epoch value.
-timeend | Optional name of the time end field, needs to be date/time data type. If set, then annotations are marked as regions between time and time-end.
+timeend | Optional name of the time end field, needs to be date/time data type. If set, then annotations are marked as regions between time and time-end. (Grafana v6.6+)
 text | Event description field.
 tags | Optional field name to use for event tags as a comma separated string.