Question

我再次陷入MySQL查询，我想要一些帮助。

我正在努力找到最好的方法来做到这一点。我想要做的是检查$ var ='x'并根据它运行不同的查询。

部分代码：

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..

连接很多。有一个更好的方法吗？几乎每个变量（共7个）都有3种不同的选择。我不能把var = $var放在WHERE子句下面，因为有时$var = '0'我的意思是所有的结果所以我甚至没有把它放在那里..

这是一个过滤脚本/代码..

这对你有意义吗？谢谢！

Answer 1

我认为这可以通过单个查询和不同的WHERE条件来完成。您需要首先定义何时将var1 = ''放入WHERE子句中。当您在查询中逐一需要varX = ''时，您应该找出案例。

$conds = array();
if ($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

怎么样：

$where_parts = array();
if (isset($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

您是否有可能只专注于与查询相关的变量？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";

它可能不是代码最优化的，但很容易理解。

使用where子句和if语句进行MySQL查询

3 个答案: