php - 在同一查询中搜索所有内容

Question

表(书)==>(keyid,name)

<form action="se.php">
    <select>
    <option value="1">book1</option>
    <option value="2">book2</option>
    <option value="3">book3</option>
    <option value="????">All Book</option>
    </select>
<input type="submit" name="search" value="search">
</form>

//se.php 
    $keyid=$_GET[keyid];
    $sql=mysql_query("SELECT `name` FROM `book` WHERE `keyid`='$keyid'");
//end page

我在最后一个选项值 (????) 中输入了什么用于 sql 查询搜索所有内容？？？

Answer 1

全部

然后:

$where = '';

if $keyid != all then {
  $where = WHERE `keyid`= $keyid // escape value protect from sql injection!
}

mysql_query("SELECT `name` FROM `book` $where");