Sql Having Sql Func Mid Sql Between Sql Drop Sql Wildcards Sql Join Inner Sql Join Full Sql Func Lcase Sql Where Sql Join Sql Func Round Sql Primarykey Sql Func First Sql Func Len Sql Distinct Sql Func Ucase Sql Function Sql Delete Sql Autoincrement Func Curtime Sql Update Sql Isnull Func Date Sub Sql Constraints Sql Intro Sql Dates Sql Select Into Sql Hosting Sql Create Table Sql Func Format Sql View Sql Func Count Sql Index Sql Like Sql Datatypes General Sql Datatypes Func Convert Sql Func Avg Sql Foreignkey Sql Func Sum Sql Join Right Func Curdate Sql Alias Sql Union Func Date Add Sql Groupby Sql Summary Sql In Sql Null Values Sql Syntax Sql Tutorial Sql Insert Into Select Sql And Or Sql Join Left Sql Func Now Func Date Sql Top Index Sql Create Db Sql Unique Sql Check Func Extract Sql Alter Sql Notnull Func Now Sql Select Sql Insert Sql Func Max Sql Exists Sql Func Min Func Date Format Func Datediff Mysql Func Getdate Sql Orderby Func Datediff Sql Func Last Sql Create Index Func Dateadd Sql Quickref Func Datepart

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | 淘宝          | https://www.taobao.com/   | 13    | CN      |
| 3  | tutorialpro.org      | http://www.tutorialpro.org/    | 5000  | CN      |
| 4  | 微博          | http://weibo.com/         | 20    | CN      |
| 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |
|  6 | 百度         | https://www.baidu.com/    |     4 | CN      |
|  7 | stackoverflow | http://stackoverflow.com/ |     0 | IND     |
+----+---------------+---------------------------+-------+---------+

SELECT MAX(alexa) AS max_alexa FROM Websites;