查询语句问题,WHERE 附近的语法不正确

Query statement issue , incorrect syntax near WHERE

 con.Open();
 string query = "INSERT INTO userinfo(username, Name, Phone, Email, Address, Postalcode) values (@username, @Name, @phone, @email, @Address, @postalcode) WHERE username =" + username;

错误报告:

incorrect syntax near WHERE

SQL INSERT 语句不支持 WHERE 子句。 我假设您正在寻找 UPDATE 语句。

https://www.w3schools.com/sql/sql_update.asp