feat: add sql solution to lc problem: No.1112 (doocs#800)

No.1112.Highest Grade For Each Student

Author: Dhoni77

solution/1100-1199/1112.Highest Grade For Each Student/README.md

@@ -63,7 +63,15 @@ Enrollments 表：
 ### **SQL**
 
 ```sql
-
+SELECT
+  student_id,
+  course_id,
+  grade
+FROM (SELECT
+  *,
+  RANK() OVER (PARTITION BY student_id ORDER BY grade DESC, course_id) rk
+FROM Enrollments) a
+WHERE a.rk = 1;
 ```
 
 <!-- tabs:end -->

solution/1100-1199/1112.Highest Grade For Each Student/README_EN.md

@@ -59,7 +59,15 @@ Enrollments table:
 ### **SQL**
 
 ```sql
-
+SELECT
+  student_id,
+  course_id,
+  grade
+FROM (SELECT
+  *,
+  RANK() OVER (PARTITION BY student_id ORDER BY grade DESC, course_id) rk
+FROM Enrollments) a
+WHERE a.rk = 1;
 ```
 
 <!-- tabs:end -->

solution/1100-1199/1112.Highest Grade For Each Student/Solution.sql

@@ -0,0 +1,9 @@
+SELECT
+  student_id,
+  course_id,
+  grade
+FROM (SELECT
+  *,
+  RANK() OVER (PARTITION BY student_id ORDER BY grade DESC, course_id) rk
+FROM Enrollments) a
+WHERE a.rk = 1;