Add "state x days ago" query (#27028)

Co-authored-by: Franck Nijhof <frenck@frenck.nl>
Co-authored-by: G Johansson <goran.johansson@shiftit.se>

source/_integrations/sql.markdown

@@ -186,6 +186,31 @@ WHERE
 ```
 Use `state` as column for value.
 
+### State of an entity x time ago
+
+If you want to extract the state of an entity from a day, hour, or minute ago, the query is:
+
+```sql
+SELECT 
+  states.state
+FROM 
+  states 
+  INNER JOIN states_meta ON 
+    states.metadata_id = states_meta.metadata_id
+WHERE 
+  states_meta.entity_id = 'sensor.temperature_in' 
+  AND last_updated_ts <= strftime('%s', 'now', '-1 day')
+ORDER BY 
+  last_updated_ts DESC 
+LIMIT
+  1;
+```
+
+Replace `-1 day` with the target offset, for example, `-1 hour`.
+Use `state` as column for value.
+
+Keep in mind that, depending on the update frequency of your sensor and other factors, this may not be a 100% accurate reflection of the actual situation you are measuring. Since your database won’t necessarily have a value saved exactly 24 hours ago, use “>=” or “<=” to get one of the closest values.
+
 ### Database size
 
 #### Postgres