我想创建一个简单的收藏夹的应用程序，在那里你可以保持您的收藏夹页面（从网站为例）。

I'm trying to create a simple favorites application, where you can keep your favorites pages (from the web for example).

让我们说我有以下数据在我的数据库

Let's say I have the following data in my database

Title    | URL     | TAG      |
-------------------------------
Hey       Ho.com    Site
Jo        Jo.com    Image
Jo        Mo.com    Image

现在我要确保，在用户不添加同一页面两次，所以我会检查该值已经存在。但我需要的用户没有一个网站添加到已添加的表。

Now I want to make sure, the user does not add the same page twice, so I will check if the value already exists. But I need to that the user does not add a site to the table that has already been added.

现在，让我们说，我会尝试添加：

So let's say I would try to add:

Title    | URL     | TAG      |
-------------------------------
Jo        Mo.com    Image

这会返回true（即检查是否存在排，因为一个相同的行已存在）。

This it would return true (for "check if row exist", because an identical row already exists).

但是，如果我会尝试添加：

But if I would try to add:

Title    | URL     | TAG      |
-------------------------------
Jo        Go.com    Image

有将返回false（虽然标题已经存在），因为没有相同行

It would return false (though the title already exists), because there is no identical row.

这是在code其中添加我的数据到数据库：

This is the code where I add my data to the database with:

public long createNote(String title, String url, String rn) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_TITLE, title);
    initialValues.put(KEY_URL, url);
    initialValues.put(KEY_RN, rn);

    return mDb.insert(DATABASE_TABLE, null, initialValues);

我如何检查是否已存在某行的数据库？

How can I check if a row already exists in a database?

推荐答案

您可以检查使用光标：

public boolean checkEvent(String title, String URL, String tag) 
{
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLES, 
            new String[] { KEY_TITLE,KEY_URL,KEY_TAG }, 
            KEY_TITLE + " = ? and "+ KEY_URL + " = ? and " + KEY_TAG + " = ?" , 
            new String[] {title,url,tag}, 
            null, null, null, null);

    if(cursor.moveToFirst())

     return true; //row exists
    else 
     return false;

}

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