偏移量和限制的 SQLite 分页问题

Question

我正在进行如下查询以在一页中加载 10 个引号

arrayList.addAll(db.loadFav(CURRENT_PAGE, Constant.ITEM_PER_PAGE));

和DBHelper.loadFav如下所示

 public ArrayList<ItemQuotes> loadFav(int offset, int limit) {
        ArrayList<ItemQuotes> arrayList = new ArrayList<>();
        try {
            //Cursor cursor = db.query(TABLE_QUOTES_FAV, columns_quotes, null, null, null, null, null);
            String query = "SELECT * FROM " + TABLE_QUOTES_FAV + " ORDER BY " + TAG_QUOTES_ID + " ASC "+ " LIMIT " + offset+","+limit;
            Cursor cursor = db.rawQuery(query, null);
            if (cursor != null && cursor.moveToFirst()) {
                Log.e("ABC", cursor.getCount() + "");
                for (int i = 0; i < cursor.getCount(); i++) {
    
                    String qid = cursor.getString(cursor.getColumnIndex(TAG_QUOTES_ID));
                    String quotes = cursor.getString(cursor.getColumnIndex(TAG_QUOTES));
                    String cid = cursor.getString(cursor.getColumnIndex(TAG_CAT_ID));
                    String cname = cursor.getString(cursor.getColumnIndex(TAG_CAT_NAME));
                    String quote_time = cursor.getString(cursor.getColumnIndex(TAG_QUOTE_TIME));
    
                    ItemQuotes itemQuotes = new ItemQuotes(qid, quotes, cid, cname, quote_time);
                    arrayList.add(itemQuotes);
    
                    cursor.moveToNext();
                }
                cursor.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    
        return arrayList;
    }

在第一次通话中 When CURRENT_PAGE=1, its loading 10 Quotes, WHEN CURRENT_PAGE= 2, its loading 9 Quotes and so on for next...但是我在 Table 中只有 11 个报价...我不知道这有什么问题以及如何解决它。让我知道这里是否有人可以帮助我解决问题。谢谢！

Answer 1

String query = "SELECT * FROM " + TABLE_QUOTES_FAV + " ORDER BY " + TAG_QUOTES_ID + " ASC "+ " LIMIT " + limit + " OFFSET "+ offset;

查询样本

SELECT * FROM
TABLE_QUOTES_FAV  LIMIT 10 OFFSET 20

Answer 2

当CURRENT_PAGE=1你想要OFFSET是0，当CURRENT_PAGE=2你想要OFFSET是10等等。
您正在做的是将 CURRENT_PAGE 传递给 loadFav() 的参数 offset，因此您将 CURRENT_PAGE 用作 offset.
您应该将 offset 计算为：

(CURRENT_PAGE - 1) * Constant.ITEM_PER_PAGE

因此，将您的 sql 语句更改为：

String query = 
    "SELECT * FROM " + TABLE_QUOTES_FAV + " ORDER BY " + TAG_QUOTES_ID + " ASC " + 
    "LIMIT " + ((offset - 1) * limit) + "," + limit;

但正确的做法是将 loadFav() 的第一个参数的名称从 offset 更改为 currentPage:

loadFav(int currentPage, int limit)

以便清楚该参数代表什么并使用变量：

int offset = (currentPage - 1) * limit;

然后您可以在代码中使用您的 sql 语句。

偏移量和限制的 SQLite 分页问题

SQLite Paging issue with Offset and Limit

java

sqlite

android

android-sqlite