我在MySQL中有一个存储多边形的表。我可以使用以下查询在命令行上重新阅读:
mysql> SELECT polygonid, AsText(thepolygon) FROM polygons;
+-----------+----------------------------------------------------------------------------------------------------------------+ | polygonid | AsText(thepolygon) |
+-----------+----------------------------------------------------------------------------------------------------------------+ | 1 | POLYGON((36.96318 127.002881,37.96318 127.002881,37.96318
128.002881,36.96318 128.002881,36.96318 127.002881)) | +-----------+----------------------------------------------------------------------------------------------------------------+ 1 row in set, 1 warning (0.02 sec)
当我尝试使用相同的查询在PHP中阅读此内容时,多边形会正确返回,但是多边形会返回为空:
$query = "SELECT polygonid, AsText(thepolygon) FROM polygons";
$result = mysqli_query($con, $query);
while ($row = mysqli_fetch_array($result)) {
var_dump($row['polygonid']);
var_dump($row['thepolygon']);
[...]
产生
string(1) "1" NULL
表示'thepolygon'返回为NULL,但是'polygonid'返回很好。
如果我将查询更改为
SELECT polygonid, thepolygon FROM polygons
然后我得到了二进制数据:
string(1) "1" string(97)
"�t{I{B@�1�3/�_@�t{I�B@�1�3/�_@�t{I�B@��`@�t{I{B@��`@�t{I{B@�1�3/�_@"
string
几乎就像astext()不起作用。 我在做什么错了?
完全感谢任何输入!
答案 0 :(得分:1)
可能只是因为您没有为int main( int argc, char **argv )
{
// vary this to find optimal size
// (must be a multiple of page size)
size_t copy_size = 1024UL * 1024UL;
// get a page-aligned buffer
char *buffer;
::posix_memalign( &buffer, ( size_t ) ( 4UL * 1024UL ), copy_size );
// make sure the entire buffer's virtual-to-physical mappings
// are actually done (can actually matter with large buffers and
// extremely fast IO systems)
::memset( buffer, 0, copy_size );
fd = ::open( argv[ 1 ], O_RDONLY | O_DIRECT );
for ( ;; )
{
ssize_t bytes_read = ::read( fd, buffer, copy_size );
if ( bytes_read <= 0 )
{
break;
}
}
return( 0 );
}
选择项提供可以从PHP数组中提取的别名。
如果您打印出AsText()
,则可能会发现您的阵列没有$row
键。
您尝试过吗?
thepolygon
它在命令行上有效,因为您只是打印出查询中选择的任何内容,但是在PHP中,您试图打印出数组键-即所选字段的名称。您的MySQL查询不会选择名为$query = "SELECT polygonid, AsText(thepolygon) AS thepolygon FROM polygons";
的字段,因此该数组也不存在。