Question

嘿，我有一个问题。如何从后向读取我的Sql数据。我尝试了很多我在网上找到的东西，但这里没有任何作用是我的代码：

public Cursor getAllRows() {
    String where = null;
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                        where, null, null, null,null,null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;

Cursor的代码：

Cursor cursor = myDb.getAllRows();

// Allow activity to manage lifetime of the cursor.
// DEPRECATED! Runs on the UI thread, OK for small/short queries.
startManagingCursor(cursor);

// Setup mapping from cursor to view fields:
String[] fromFieldNames = new String[] 
        {DBAdapter.KEY_KALO, DBAdapter.KEY_HYDRATE, DBAdapter.KEY_FAT, DBAdapter.KEY_PROTEIN ,DBAdapter.KEY_CAL};
int[] toViewIDs = new int[]
        {R.id.item_Kalorien,     R.id.item_KG_in_g,           R.id.item_F_in_g,     R.id.item_P_in_g,R.id.item_cal};

// Create adapter to may columns of the DB onto elemesnt in the UI.
SimpleCursorAdapter myCursorAdapter = 
        new SimpleCursorAdapter(
                this,       // Context
                R.layout.item_tagebuch, // Row layout template
                cursor,                 // cursor (set of DB records to map)
                fromFieldNames,         // DB Column names
                toViewIDs               // View IDs to put information in
                );

// Set the adapter for the list view
ListView myList = (ListView) findViewById(R.id.listView1);
myList.setAdapter(myCursorAdapter);

坦克你的帮助，抱歉我的英语不好：）

Answer 1

“从后向”的陈述含糊不清我假设你想以特定的顺序阅读db

如果你想按字段的降序读取'foo'然后

String ORDER = "foo DESC";/*use ASC for ascending order*/

并更改鳕鱼如下

public Cursor getAllRows() {
    String where = null;
    String Order = "foo DESC";
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                        where, null, null, null,Order,null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;

以下是查询

的语法

public Cursor query (String table, String[] columns, String selection,String[] selectionArgs, String groupBy, String having, String orderBy, String limit)

有关进一步说明，请参阅以下链接 SQLiteDatabase Android

Answer 2

向后是一个奇怪的词，但我认为你需要对数据进行排序，所以这里是

1。在获取数据前排序

可以使用 ORDER BY 关键字来完成。 db.query（）方法中的最后一个参数是order by子句（没有＆＃34; order by＆＃34;关键字）。

因此请将您的查询更改为

Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                    where, null, null, null,null,COLUMN_NAME + " ASC");

ASC用于按升序排序和DESC用于降序

如果你想要多种颜色，那么就这样做

Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                    where, null, null, null,null,COLUMN_NAME + " ASC, " +COLUMN_NAME2 + " DESC");

2. 获取数据后的排序

如果您在获取数据后尝试对其进行排序，则应在光标级别

完成

Cursor cursor = myDb.getAllRows();
if (cursor.moveToFirst()) {
    do {
    // do what you need with the cursor here
    } while (cursor.moveToNext());
}

OR REVERSE

if (cursor.moveToLast()) {
    do {
    // do what you need with the cursor here
    } while (cursor.moveToPrevious());
}

从后向读取SQL数据库

2 个答案: