feat: update sql solution to lc problem: No.1294 (doocs#1811)

Author: thinkasany

solution/1200-1299/1294.Weather Type in Each Country/README.md

@@ -122,15 +122,15 @@ Morocco 11 月的平均 weather_state 为 (25 + 27 + 31) / 3 = 27.667 所以天
 SELECT
     country_name,
     CASE
-        WHEN avg(weather_state) <= 15 THEN 'Cold'
-        WHEN avg(weather_state) >= 25 THEN 'Hot'
+        WHEN AVG(weather_state) <= 15 THEN 'Cold'
+        WHEN AVG(weather_state) >= 25 THEN 'Hot'
         ELSE 'Warm'
     END AS weather_type
 FROM
     Weather AS w
-    JOIN Countries AS c ON w.country_id = c.country_id
-WHERE date_format(day, '%Y-%m') = '2019-11'
-GROUP BY w.country_id;
+    JOIN Countries USING (country_id)
+WHERE DATE_FORMAT(day, '%Y-%m') = '2019-11'
+GROUP BY 1;
 ```
 
 <!-- tabs:end -->

solution/1200-1299/1294.Weather Type in Each Country/README_EN.md

@@ -117,15 +117,15 @@ We know nothing about the average weather_state in Spain in November so we do no
 SELECT
     country_name,
     CASE
-        WHEN avg(weather_state) <= 15 THEN 'Cold'
-        WHEN avg(weather_state) >= 25 THEN 'Hot'
+        WHEN AVG(weather_state) <= 15 THEN 'Cold'
+        WHEN AVG(weather_state) >= 25 THEN 'Hot'
         ELSE 'Warm'
     END AS weather_type
 FROM
     Weather AS w
-    JOIN Countries AS c ON w.country_id = c.country_id
-WHERE date_format(day, '%Y-%m') = '2019-11'
-GROUP BY w.country_id;
+    JOIN Countries USING (country_id)
+WHERE DATE_FORMAT(day, '%Y-%m') = '2019-11'
+GROUP BY 1;
 ```
 
 <!-- tabs:end -->

solution/1200-1299/1294.Weather Type in Each Country/Solution.sql

@@ -1,13 +1,12 @@
-# Write your MySQL query statement below
 SELECT
     country_name,
     CASE
-        WHEN avg(weather_state) <= 15 THEN 'Cold'
-        WHEN avg(weather_state) >= 25 THEN 'Hot'
+        WHEN AVG(weather_state) <= 15 THEN 'Cold'
+        WHEN AVG(weather_state) >= 25 THEN 'Hot'
         ELSE 'Warm'
     END AS weather_type
 FROM
     Weather AS w
-    JOIN Countries AS c ON w.country_id = c.country_id
-WHERE date_format(day, '%Y-%m') = '2019-11'
-GROUP BY w.country_id;
+    JOIN Countries USING (country_id)
+WHERE DATE_FORMAT(day, '%Y-%m') = '2019-11'
+GROUP BY 1;