带where子句和if语句的MySQL查询

Question

我再次陷入了MySQL查询中，我希望得到一些帮助。

我正试图找到最好的方法来做这件事。我想要做的是检查$var = 'x‘，并在此基础上运行不同的查询。

守则的一部分：

if ($var1 == '0' AND $var2 != '0' AND $var3 != '0' AND $var4 != '0') {
    echo $query = "SELECT * FROM table WHERE var1 = ''";
}elseif ($var1 == '1' AND $var2 != '0' AND $var3 != '0' AND $var4 != '0') {
    echo $query = "SELECT * FROM table WHERE var1 = '1'";
}elseif ($var1 != '0' AND $var2 == '0' AND $var3 != '0' AND $var4 != '0') {
    echo $query = "SELECT * FROM table WHERE var2 = ''";
}elseif ($var1 == '0' AND $var2 == '0' AND $var3 != '0' AND $var4 != '0') {
    echo $query = "SELECT * FROM table WHERE var1 = '' AND var2 = ''";
} etc..

有很多联系。有更好的方法吗？几乎每个变量(总共7个)都有3种不同的选择。我不能把var = $var放在WHERE子句下，因为有时候$var = '0'是指所有的结果，所以我甚至不把它放在那里。

顺便说一下，这是一个过滤脚本/代码。

这对你来说有意义吗？谢谢!

Answer 1

我认为这可以通过一个查询和变化的条件来完成。您需要首先定义何时将var1 = ''放在WHERE子句中。当您在查询中需要varX = ''时，您应该逐一查找这些情况。

$conds = array();
if ($var1 == '0' || $var2 == '0') {
  $conds[] = "var1 = ''"; // this should be the only point where var1 is included in your query, so you need to have every possible condition in this if part
}
if ($var3 == '0' && $var4 != '0') {
  $conds[] = "var3 = ''";
}
// ..etc..
$query = "SELECT * FROM TABLE WHERE " . implode(' AND ', $conds);

Answer 2

不如：

$where_parts = array();
if (isset($var1)) {
  if ($var1 == 0) { $var1 = ''; }
  $where_parts [] = "var1 = '" . $var1 . "'";
}
if (isset($var2)) {
if ($var2 == 0) { $var2 = ''; }
  $where_parts [] = "var2 = '" . $var2 . "'";
}
if (isset($var3)) {
if ($var3 == 0) { $var3 = ''; }
  $where_parts [] = "var3 = '" . $var3 . "'";
}
if (isset($var4)) {
if ($var4 == 0) { $var4 = ''; }
  $where_parts [] = "var4 = '" . $var4 . "'";
}

$query = "SELECT * FROM table WHERE " . implode(' AND ', $where_parts );

Answer 3

您是否可能只关注与查询相关的变量？例如：

$str = "";

# When will "var1" be in the query
switch($var1) {
  case '0' : $str .= " AND $var1=''"; break;
  case '1' : $str .= " AND $var1='1'"; break;
}

# When will "var2" be in the query
switch($var2) {
  case '0' : $str .= " AND $var2=''"; break;
  case '1' : $str .= " AND $var2='1'"; break;
}

...

# If not empty then remove the first " AND "
if(!empty($str)) {
    $str = substr($str,4);
}

# Final query is a lot of concatenated strings
$query = "SELECT * FROM table WHERE $str";

它可能不是最优化的代码，但它很容易理解。