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一、truncate 截断truncate table [TableName] //截断当前数据到之前。相当于清空。主键重置。二、DISTINCT 去重select *, count(distinct name) from table group by name三、Mysql字符串截取函数SUBSTRING的用法说明函数： 1、从左开始截取字符串 left（str, length） 说明：left
MYSQL下建立视图第一类：create view v as select * from table; 第二类：create view v as select id,name,age from table; 第三类：create view v[vid,vname,vage] as select id,name,age from table; 如
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