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<body>
<table width="760" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td><img src="images/bg_01.jpg" width="760" height="254" /></td>
</tr>
<tr>
<td align="center"><table width="700" border="0">
<tr>
<td width="78" align="center"><span class="STYLE1">ID</span></td>
<td width="262" align="center"><span class="STYLE1">图书名称</span></td>
<td width="77" align="center"><span class="STYLE1">价格</span></td>
<td width="176" align="center"><span class="STYLE1">出版日期</span></td>
<td width="85" align="center"><span class="STYLE1">类 型</span></td>
</tr>
<?php
include_once("conn/conn.php");
$result=mysqli_query($conn,"select * from tb_demo01");
while($myrow=mysqli_fetch_array($result)){
?>
<tr>
<td align="center"><span class="STYLE2"><?php echo $myrow[0]; ?></span></td>
<td align="left"><span class="STYLE2"><?php echo $myrow[1]; ?></span></td>
<td align="center"><span class="STYLE2"><?php echo $myrow[2]; ?></span></td>
<td align="center"><span class="STYLE2"><?php echo $myrow['date']; ?></span></td>
<td align="center"><span class="STYLE2"><?php echo $myrow['type']; ?></span></td>
</tr>
<?php
}
?>
</table></td>
</tr>
<tr>
<td><img src="images/bg_09.jpg" width="760" height="34" /></td>
</tr>
</table>
</body>
$sqlstr1 = "insert into tb_demo02 values('','$_POST[bookname]','$_POST[price]','$_POST[f_time]','$_POST[type]')";
$sqlstr1 = "insert into tb_demo02 values('','".$_POST['bookname']."','".$_POST['price']."','".$_POST['f_time']."','".$_POST['type']."')";
我想知道这个数据库插入语句中values后面跟的第一个''是代表空值,那第二个'"代表什么啊,还有后面为什么在.连接符的前后都要带一个单引号和一个双引号啊