Question

String sql = "select * from login where name='"+username+"' and password='"+password+"'";

语句中加号请问是什么意思

Answer 1

username和password是varchar类型变量

实际翻译过来就是
where name='username' and password='password' ";
+号其实就是字符串的拼接

Answer 2

username和password是变量，使用加号连接字符串