SQL 基本操作 删除 修改 刷新

SQL的操作：
E.g.
judging-表名
userid, name, password-表中的关键字
添加：
string sql = "insert into judging (userid,name,password) values('" + userid.Text.Trim() + "','" + name.Text.Trim() + "','" + password.Text.Trim() + "')";
 
删除：
string sql = "delete from judging where userid=" + app.value;
修改：
string sql = "update judging set name='"+modifyname+"',password='"+modifypsw+"'where userid=" + app.value ;
查询：
sql = "select * from judging where name='" + comboBoxName.Text + "' and userid='" + comboBoxID.Text + "'";      
更新：
string sql = "select userid as userid,name as name from judging";