mysql中length函数怎么使用

示例分析：

选自“Websites”表的数据：

+----+--------------+---------------------------+-------+---------+|id|name|url|alexa|country|+----+--------------+---------------------------+-------+---------+|1|Google|https://www.google.cm/|1|USA||2|淘宝|https://www.taobao.com/|13|CN||3|菜鸟教程|http://www.runoob.com/|4689|CN||4|微博|http://weibo.com/|20|CN||5|Facebook|https://www.facebook.com/|3|USA||7|stackoverflow|http://stackoverflow.com/|0|IND|+----+---------------+---------------------------+-------+---------+

从“Websites”表中选取“name”和“url”列中值的长度，执行以下SELECT语句：

SELECT name, LENGTH(url) as LengthOfURL
FROM Websites;

执行结果如下：