用注释的代码就出错？原理不是一样的么？
public Boolean isHasInDB ( String name , String password )
{
Connection con = connetionDB.getConnetionDB ();
Statement controlDB = null;
//String SQL = "select Password from Card where Id = "+ name;//为什么这样就会出错？？？？？？？？？？
String SQL = "select Id from Card where Password = " + password;
try
{
controlDB = con.createStatement ();
ResultSet rsDB = controlDB.executeQuery ( SQL );
while ( rsDB.next () )
{
//if ( rsDB.getString ( 1 ).equals ( password ) )//为什么这样就会出错？？？？？？？？？？
if ( rsDB.getString ( 1 ).equals ( name ) )
{
rsDB.close ();
con.close ();
controlDB.close ();
return true;
}
}
rsDB.close ();
con.close ();
controlDB.close ();
}
catch ( SQLException ex )
{
//return false;
ex.printStackTrace ();
}
return false;
}
真的非常奇怪
按密码来查找就没问题
按名字来查找的话就说没有这列...........
我的名字和密码在SQL里的数据类型是carchar(50)
求高人指点迷津
[解决办法]
应该都会出错的
"select Password from Card where Id = ' "+ name + " ' ";
"select Id from Card where Password = ' "+ Password + " ' ";
[解决办法]
//String SQL = "select Password from Card where Id = "+ name;//为什么这样就会出错？？？？？？？？？？
varchar 型 要加单引号，按密码查询不出错有可能数据库中密码的类型不是varchar,仔细检查一下
"select Password from Card where Id = ' "+ name + " ' ";
"select Id from Card where Password = ' "+ Password + " ' ";
在他后面增加一个输出语句
System.out.println(sql);
把输出的sql复制用数据库查询
