PHP & MYSQL：我如何忽略选择中的空变量

Question

如果我有 4 个变量并且我想从数据库中选择 DISTINCT 值

<?php
$var1 = ""; //this variable can be blank
$var2 = ""; //this variable can be blank
$var3 = ""; //this variable can be blank
$var4 = ""; //this variable can be blank

$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE **keywords ='$var1' OR author='$var2' OR date='$var3' OR forums='$var4'** ");

?>

注意：部分或所有变量 ($var1,$var2,$var3,$var4) 可以为空

我想要什么： 我想忽略空白字段

假设 $var1 (keywords) 为空，它将选择所有空文件，但我希望 $var1 为空，结果会是这样的

$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE author='$var2' OR date='$var3' OR forums='$var4' ");

如果 $var2 为空，结果会是这样的

$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE keywords ='$var1' OR date='$var3' OR forums='$var4' ");

如果 $var1 和 $var2 为空，结果会是这样的

$result = mysql_query("SELECT DISTINCT title,description FROM table WHERE date='$var3' OR forums='$var4' ");

等等

Answer 1

试试这个。

$vars = array(
  'keywords' => '', // instead of var1
  'author' => '',  // instead of var2
  'date' => '', // instead of var3
  'forums' => '', // instead of var4
);

$where = array();
foreach ($vars as $varname => $varvalue) {
  if (trim($varvalue) != '') $where[] = "`$varname` = '" . mysql_real_escape_string($varvalue) . "'";
}
$result = mysql_query("SELECT DISTINCT title, description FROM table WHERE " . join(" OR ", $where));

Answer 2

非常感谢每一个人experimentX ..您的回答帮助我获得了正确的功能p>

$vars = array(
        (!empty($_GET["var1"]))? " keyword = '". $_GET["var1"] ."' ": null, 
        (!empty($_GET["var2"]))? " author  = '". $_GET["var2"] ."' ": null,
        (!empty($_GET["var3"]))? " date    = '". $_GET["var3"] ."' ": null,
        (!empty($_GET["var4"]))? " forums  = '". $_GET["var4"] ."' ": null
    );


function myfilterarray($var)
{
    return !empty($var)?$var: null;
}

$newvars = array_filter($vars, 'myfilterarray');

$where = join(" OR ", $newvars);

$sql = "SELECT DISTINCT title, description FROM table ".(($where)?"WHERE ".$where: null);

echo $sql;

如果有空变量，这个函数会被忽略

再次感谢大家的有益建议

Answer 3

在调用 mysql_query(...) 之前创建您的 select 语句字符串，因此请按照以下内容执行操作：

$queryString = "Select DISTINCT title, description FROM table WHERE";
if(!empty($var1))
   $queryString .= " keywords = $var1";

等等所有变量。您还可以实现一个 for 循环并循环通过您的 $var1 - $var# 并检查 !empty($var#)

Answer 4

为什么不简单地构建一个 if else 结构？ 喜欢

if ($var1!="" && $var2!="" && $var3!="" && $var4!=""){
   $result = mysql_query("SELECT DISTINCT title,description FROM table WHERE keywords ='$var1' OR author='$var2' OR date='$var3' OR forums='$var4' ")
} else if ($var2!="" && $var3!="" && $var4!=""){
   $result = mysql_query("SELECT DISTINCT title,description FROM table WHERE author='$var2' OR date='$var3' OR forums='$var4' ");
} else if {
...
}

Answer 5

（我刚刚在他的重复帖子中发布了以下内容，所以我在这里重新发布以下内容）

如果有任何问题，请原谅我，现在已经很晚了，我只是在 Windows 上的记事本中输入了这个，没有测试环境。 * 谨慎使用 * :)

$vars = array(
'blah1' => '',
'blah2' => '',
'blah3' => '',
);

 $sql_statement = "SELECT first, last FROM names WHERE";

 $clause = "";
 foreach($vars as $k=$v)
{
$k = trim($k);
if(!empty($k))
{
    $clause .= " `$k` = '$v' OR";
}
}
$clause = rtrim($clause, "OR");

// $clause should have what you want.

Answer 6

嗯，有很多方法可以做到这一点，但我发现最短的方法是创建以下形式的数组

$vars = array(
        (isset($_GET["var1"]))? " keyword = '". $_GET["var1"] ."' ": null, 
        (isset($_GET["var2"]))? " author  = '". $_GET["var2"] ."' ": null,
        (isset($_GET["var3"]))? " date    = '". $_GET["var3"] ."' ": null,
        (isset($_GET["var4"]))? " forums  = '". $_GET["var4"] ."' ": null
    );

function myfilterarray($var)
{
    return !empty($var)?$var: null;
}

$newvars = array_filter($vars, 'myfilterarray');

$where = join(" OR ", $newvars);

$sql = "SELECT DISTINCT title, description FROM table ".(($where)?"WHERE ".$where: null);

echo $sql;

http://localhost/?var1=sadfsadf&var2=sadfasdf&var3=asdfasdf 的结果

 SELECT DISTINCT title, description FROM table WHERE keyword = 
 'sadfsadf' OR author = 'sadfasdf' OR date = 'asdfasdf' 

http://localhost/? 的结果

SELECT DISTINCT title, description FROM table