Question

我有一个Query，我试图在SQLite表上执行。表中有记录，它们映射到我传递的选择参数。以下是我的查询和全局字符串：

 // Table Notifications
    public static final String  notificationfor = "NotificationFor";
    public static final String  datetonotify = "DateToNotify";
    public static final String  isextraordinary = "IsExtraordinary";
    public static final String  notificationdata = "NotificationData";
    public static final String  notificationdatefor= "NotificationDateFor";
    public static final String  primaryid= "PrimaryId"; 


Cursor c = mDb.rawQuery("select DateToNotify from " + DATABASE_TABLE1 + 
            " where " + primaryid + " = ? AND  " + notificationfor + " = ?", new String[] { D, selection });

如果我将1和1作为参数传递（记录映射到我传递的参数），它会在游标中给出一个null

然而，当我执行以下查询时，它完美无缺：

String Tets = "Select DateToNotify from Notifications WHERE PrimaryId = 1 AND NotificationFor =1";
        Cursor c = mDb.rawQuery(Tets, null);

修改

我刚试过以下内容并且有效：

String Tets = "Select DateToNotify from Notifications WHERE PrimaryId =" +D+ " AND NotificationFor ="+selection;
        Cursor c = mDb.rawQuery(Tets, null);

整个功能如下：

public Cursor alertQueryYYYY(String D, String selection){

    //  Cursor c = mDb.rawQuery("select DateToNotify from " + DATABASE_TABLE1 + 
    //      " where " + primaryid + " = ? AND  " + notificationfor + " = ?", new String[] { D, selection });

        String Tets = "Select DateToNotify from Notifications WHERE PrimaryId =" +D+ " AND NotificationFor ="+selection;
        Cursor c = mDb.rawQuery(Tets, null); 


        String K = "select DateToNotify from " + DATABASE_TABLE1 + 
                        " where " + primaryid + " = ? AND  " + notificationfor + " = ?"; // new String[] { D, selection })

        System.out.println("Here I am " + K); 
        return c;

    }

This is the image of my table, as I dont have a good image edit software so I uploaded it on another website for clarity reasons.

修改以下是数据库创建字符串和CL指出的错误，错误在于类型不匹配。

private static final String DATABASE_CREATE1 ="create table Notifications(_id integer primary key autoincrement, "
            +"NotificationFor Integer," // Weeks/Seconds etc /7 variables
            +"DateToNotify text,"       // Date of Notification
            +"isExtraordinary Integer," // Special notifications, yet unknown
            +"NotificationData Integer," // Weeks/Seconds/ etc / 7 variables
            +"NotificationDateFor text,"
            +"PrimaryId);";

Answer 1

数字1与字符串"1"不同，因此如果您搜索错误类型的ID，则无法找到该记录。

查询参数有助于避免格式化问题和SQL注入攻击。这些问题只能出现在字符串中，而不能出现在普通整数上，因此要在查询中使用整数值，不应使用参数，只需直接插入值：

"... WHERE PrimaryId =" +D+ " AND NotificationFor ="+selection;

Answer 2

我更喜欢这种方式来使用查询：

final SQLiteDatabase database = getReadableDatabase();
 final String[] projection = new String[] {datetonotify };
 final String selection = primaryid + "=? " +notificationfor +"=?";
 final String[] having = new String[] {D,selection};
 Cursor cursor = database.query(DATABASE_TABLE1, projection, selection, having,
                null, null, null, null);

您的代码必须工作，如果有错误，它不在参数中，但可能在变量DATABASE_TABLE1中。

查询无法按预期工作

2 个答案: