Add solution 177 [sql]

Rank Scores

Author: yanglbme

README.md

@@ -88,6 +88,7 @@ Complete [solutions](https://github.com/doocs/leetcode/tree/master/solution) to
 | 150 | [Evaluate Reverse Polish Notation](https://github.com/doocs/leetcode/tree/master/solution/150.Evaluate%20Reverse%20Polish%20Notation) | `Stack` |
 | 153 | [Find Minimum in Rotated Sorted Array](https://github.com/doocs/leetcode/tree/master/solution/153.Find%20Minimum%20in%20Rotated%20Sorted%20Array) | `Array`, `Binary Search` |
 | 177 | [Nth Highest Salary](https://github.com/doocs/leetcode/tree/master/solution/177.Nth%20Highest%20Salary) | `SQL` |
+| 178 | [Rank Scores](https://github.com/doocs/leetcode/tree/master/solution/178.Rank%20Scores) | `SQL` |
 | 328 | [Odd Even Linked List](https://github.com/doocs/leetcode/tree/master/solution/328.Odd%20Even%20Linked%20List) | `Linked List` |
 
 

solution/178.Rank Scores/README.md

@@ -0,0 +1,116 @@
+## 分数排名
+### 题目描述
+
+编写一个 SQL 查询来实现分数排名。如果两个分数相同，则两个分数排名（Rank）相同。请注意，平分后的下一个名次应该是下一个连续的整数值。换句话说，名次之间不应该有“间隔”。
+```
++----+-------+
+| Id | Score |
++----+-------+
+| 1  | 3.50  |
+| 2  | 3.65  |
+| 3  | 4.00  |
+| 4  | 3.85  |
+| 5  | 4.00  |
+| 6  | 3.65  |
++----+-------+
+```
+
+例如，根据上述给定的 `Scores` 表，你的查询应该返回（按分数从高到低排列）：
+```
++-------+------+
+| Score | Rank |
++-------+------+
+| 4.00  | 1    |
+| 4.00  | 1    |
+| 3.85  | 2    |
+| 3.65  | 3    |
+| 3.65  | 3    |
+| 3.50  | 4    |
++-------+------+
+```
+
+### 解法
+对于每一个分数，找出表中有多少个 `>=` 该分数的不同的(distinct)分数，然后按降序排列。
+
+```sql
+# Write your MySQL query statement below
+
+select Score, (select count(distinct Score) from Scores where Score >= s.Score) Rank from Scores s order by Score desc;
+
+```
+
+#### Input
+```json
+{
+    "headers": {
+        "Scores": [
+            "Id",
+            "Score"
+        ]
+    },
+    "rows": {
+        "Scores": [
+            [
+                1,
+                3.50
+            ],
+            [
+                2,
+                3.65
+            ],
+            [
+                3,
+                4.00
+            ],
+            [
+                4,
+                3.85
+            ],
+            [
+                5,
+                4.00
+            ],
+            [
+                6,
+                3.65
+            ]
+        ]
+    }
+}
+```
+
+#### Output
+```json
+{
+    "headers": [
+        "Score",
+        "Rank"
+    ],
+    "values": [
+        [
+            4.0,
+            1
+        ],
+        [
+            4.0,
+            1
+        ],
+        [
+            3.85,
+            2
+        ],
+        [
+            3.65,
+            3
+        ],
+        [
+            3.65,
+            3
+        ],
+        [
+            3.5,
+            4
+        ]
+    ]
+}
+```