sqlite - 从 mbtiles 读取 tile-data 会生成“RangeError：错误 #2006：提供的索引超出范围。”

Question

我正在尝试从 sqlite 数据库中读取图像数据（它是一个 mbtiles 地图图块文件），因为我试图转换此 php 代码

$sql = "SELECT * FROM tiles WHERE zoom_level = $zoom AND tile_column = $column AND tile_row = $row";
$q = $conn->prepare($sql);
$q->execute();

$q->bindColumn(1, $zoom_level);
$q->bindColumn(2, $tile_column);
$q->bindColumn(3, $tile_row);
$q->bindColumn(4, $tile_data, PDO::PARAM_LOB);

while($q->fetch())
{
header("Content-Type: image/png");
echo $tile_data;
}

到 as3 使用

        _conn = new SQLConnection();
        _conn.addEventListener(SQLEvent.OPEN, openHandler); 
        _conn.addEventListener(SQLErrorEvent.ERROR, errorHandler); 
        var folder:File = File.applicationDirectory; 
        var dbFile:File = folder.resolvePath("test.mbtiles");
        _conn.openAsync(dbFile, SQLMode.READ);
        function openHandler(event:SQLEvent):void 
    { 
        trace("db opened"); 
        var selectStmt:SQLStatement = new SQLStatement(); 
        selectStmt.sqlConnection = _conn; 
        selectStmt.text = "SELECT * FROM tiles WHERE zoom_level = 5 AND tile_column = 17 AND tile_row = 20"; 
       selectStmt.execute();
    } 

但我收到“RangeError：错误 #2006：提供的索引超出范围。”

关于如何解决这个问题的任何想法？谢谢！

Answer 1

啊哈，神经兮兮的。查询应该是

"SELECT CAST(tile_data AS ByteArray) as data " +
                    "FROM tiles WHERE " +
                    "zoom_level = 5 " +
                    "and tile_column = 17 " +
                    "and tile_row = 20";