feat: add solutions to lc problems: No.1501,1532

* No.1501.Countries You Can Safely Invest In
* No.1532.The Most Recent Three Orders

Author: yanglbme

solution/1500-1599/1501.Countries You Can Safely Invest In/README.md

@@ -120,7 +120,29 @@ Result 表:
 ### **SQL**
 
 ```sql
-
+# Write your MySQL query statement below
+with t as (
+    select
+        left(phone_number, 3) as country_code,
+        avg(duration) as duration
+    from
+        Person
+        join Calls on id in (caller_id, callee_id)
+    group by
+        country_code
+)
+select
+    c.name country
+from
+    Country c
+    join t on c.country_code = t.country_code
+where
+    t.duration > (
+        select
+            avg(duration)
+        from
+            Calls
+    )
 ```
 
 <!-- tabs:end -->

solution/1500-1599/1501.Countries You Can Safely Invest In/README_EN.md

@@ -122,7 +122,29 @@ Since Peru is the only country where the average call duration is greater than t
 ### **SQL**
 
 ```sql
-
+# Write your MySQL query statement below
+with t as (
+    select
+        left(phone_number, 3) as country_code,
+        avg(duration) as duration
+    from
+        Person
+        join Calls on id in (caller_id, callee_id)
+    group by
+        country_code
+)
+select
+    c.name country
+from
+    Country c
+    join t on c.country_code = t.country_code
+where
+    t.duration > (
+        select
+            avg(duration)
+        from
+            Calls
+    )
 ```
 
 <!-- tabs:end -->

solution/1500-1599/1501.Countries You Can Safely Invest In/Solution.sql

@@ -0,0 +1,23 @@
+# Write your MySQL query statement below
+with t as (
+    select
+        left(phone_number, 3) as country_code,
+        avg(duration) as duration
+    from
+        Person
+        join Calls on id in (caller_id, callee_id)
+    group by
+        country_code
+)
+select
+    c.name country
+from
+    Country c
+    join t on c.country_code = t.country_code
+where
+    t.duration > (
+        select
+            avg(duration)
+        from
+            Calls
+    )

solution/1500-1599/1532.The Most Recent Three Orders/README.md

@@ -106,12 +106,40 @@ Marwan 只有 1 笔订单。
 
 <!-- 这里可写通用的实现逻辑 -->
 
+**方法一：窗口函数**
+
 <!-- tabs:start -->
 
 ### **SQL**
 
 ```sql
-
+# Write your MySQL query statement below
+select
+    name as customer_name,
+    o.customer_id,
+    order_id,
+    order_date
+from
+    Customers c
+    join (
+        select
+            customer_id,
+            order_date,
+            order_id,
+            rank() over(
+                partition by customer_id
+                order by
+                    order_date desc
+            ) rk
+        from
+            orders
+    ) o on c.customer_id = o.customer_id
+where
+    rk <= 3
+order by
+    name,
+    o.customer_id,
+    order_date desc;
 ```
 
 <!-- tabs:end -->

solution/1500-1599/1532.The Most Recent Three Orders/README_EN.md

@@ -105,7 +105,33 @@ We sort the result table by customer_name in ascending order, by customer_id in
 ### **SQL**
 
 ```sql
-
+# Write your MySQL query statement below
+select
+    name as customer_name,
+    o.customer_id,
+    order_id,
+    order_date
+from
+    Customers c
+    join (
+        select
+            customer_id,
+            order_date,
+            order_id,
+            rank() over(
+                partition by customer_id
+                order by
+                    order_date desc
+            ) rk
+        from
+            orders
+    ) o on c.customer_id = o.customer_id
+where
+    rk <= 3
+order by
+    name,
+    o.customer_id,
+    order_date desc;
 ```
 
 <!-- tabs:end -->

solution/1500-1599/1532.The Most Recent Three Orders/Solution.sql

@@ -0,0 +1,27 @@
+# Write your MySQL query statement below
+select
+    name as customer_name,
+    o.customer_id,
+    order_id,
+    order_date
+from
+    Customers c
+    join (
+        select
+            customer_id,
+            order_date,
+            order_id,
+            rank() over(
+                partition by customer_id
+                order by
+                    order_date desc
+            ) rk
+        from
+            orders
+    ) o on c.customer_id = o.customer_id
+where
+    rk <= 3
+order by
+    name,
+    o.customer_id,
+    order_date desc;