add leetcode

Author: wave-gbt

Database/182. Duplicate Emails.md

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+Write a SQL query to find all duplicate emails in a table named `Person`.
+
+```
++----+---------+
+| Id | Email   |
++----+---------+
+| 1  | a@b.com |
+| 2  | c@d.com |
+| 3  | a@b.com |
++----+---------+
+```
+For example, your query should return the following for the above table:
+```
++---------+
+| Email   |
++---------+
+| a@b.com |
++---------+
+```
+Note: All emails are in lowercase.
+
+**SQL**
+```
+# Write your MySQL query statement below
+select email from Person
+group by Email having count(*)>1
+```

Database/197. Rising Temperature.md

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+Given a `Weather` table, write a SQL query to find all dates' Ids with higher temperature compared to its previous (yesterday's) dates.
+
+```
++---------+------------+------------------+
+| Id(INT) | Date(DATE) | Temperature(INT) |
++---------+------------+------------------+
+|       1 | 2015-01-01 |               10 |
+|       2 | 2015-01-02 |               25 |
+|       3 | 2015-01-03 |               20 |
+|       4 | 2015-01-04 |               30 |
++---------+------------+------------------+
+```
+For example, return the following Ids for the above Weather table:
+
+```
++----+
+| Id |
++----+
+|  2 |
+|  4 |
++----+
+```
+**SQL**
+```
+# Write your MySQL query statement below  
+SELECT wt1.Id  
+    FROM Weather wt1,Weather wt2  
+    WHERE TO_DAYS(wt1.DATE)-TO_DAYS(wt2.DATE)=1  
+            &&  wt1.Temperature>wt2.Temperature;  
+```