ghostmac的专栏

 数据升序,降序:select * from Person1where age >20 order by Number asc ,age asc; 数据分组(group by):select nickname,COUNT(*) from Person1 group by NickName; 取出分组中总数大于1的字段的数量:select age,count(*)

cmd.CommandText = "select * from LogIn where username = @username and password = @password";cmd.Parameters.Add(new SqlParameter("username", userName));cmd.Parameters.Add(new SqlParameter("password

使用查询语句的时候，经常要返回前几条或者中间某几行数据，这个时候怎么办呢？不用担心，mysql已 经为我们提供了这样一个功能。SELECT* FROMtable   LIMIT[offset,] rows| rows OFFSET offset

ALTER TABLE — 更改表属性语法ALTER TABLE table [ * ]      ADD [ COLUMN ] column typeALTER TABLE table [ * ]      ALTER [ COLUMN ] column

1、MSDN上说：Sends the CommandText to the Connection and builds a SqlDataReader.                  (这句话就不翻译了)2、实例片段： [C#]public void Crea