feat: add sql solution to lc problem: No.0597 (#766)

No.0597.Friend Requests I: Overall Acceptance Rate

Author: Dhoni77

solution/0500-0599/0597.Friend Requests I Overall Acceptance Rate/README.md

@@ -102,7 +102,13 @@ RequestAccepted 表：
 ### **SQL**
 
 ```sql
-
+SELECT IFNULL(ROUND((
+		SELECT COUNT(DISTINCT requester_id, accepter_id)
+		FROM RequestAccepted
+	) / (
+		SELECT COUNT(DISTINCT sender_id, send_to_id)
+		FROM FriendRequest
+	), 2), 0.00) AS accept_rate;
 ```
 
 <!-- tabs:end -->

solution/0500-0599/0597.Friend Requests I Overall Acceptance Rate/README_EN.md

@@ -98,7 +98,13 @@ There are 4 unique accepted requests, and there are 5 requests in total. So the
 ### **SQL**
 
 ```sql
-
+SELECT IFNULL(ROUND((
+		SELECT COUNT(DISTINCT requester_id, accepter_id)
+		FROM RequestAccepted
+	) / (
+		SELECT COUNT(DISTINCT sender_id, send_to_id)
+		FROM FriendRequest
+	), 2), 0.00) AS accept_rate;
 ```
 
 <!-- tabs:end -->

solution/0500-0599/0597.Friend Requests I Overall Acceptance Rate/Solution.sql

@@ -0,0 +1,7 @@
+SELECT IFNULL(ROUND((
+		SELECT COUNT(DISTINCT requester_id, accepter_id)
+		FROM RequestAccepted
+	) / (
+		SELECT COUNT(DISTINCT sender_id, send_to_id)
+		FROM FriendRequest
+	), 2), 0.00) AS accept_rate;