php - SQL/PHP 如果不满足条件则选择所有内容

Question

我的网页上有一个输入，其中包含两个搜索参数(例如类型和位置)。当输入参数时，PHP搜索SQL数据库并输出满足输入参数的结果。

$sql = "
SELECT MainID
     , MainName
     , MainLocation
     , MainType 
  FROM Main 
 WHERE MainType = 'typeIWant' 
   AND MainLocation = 'LocationIWant' 
";

但是，当用户仅选择一个参数时，它应该显示仅满足所选参数的所有结果。

类似于:

$sql = "SELECT MainID, MainName, MainLocation, MainType FROM Main WHERE MainType= 'typeIWant' AND MainLocation = '*' ";

除非这不起作用。

它应该显示满足 MainType 的所有结果，无论其 MainLocation 是什么。

这是怎么做到的？

Answer 1

下面一行:

$sql = "SELECT MainID, MainName, MainLocation, MainType FROM Main WHERE MainType= 'typeIWant' AND MainLocation = '*' ";

正在搜索名为(或命名为)*的MainLocation

如果您只想搜索 MainType，您应该这样做:

$sql = "SELECT MainID, MainName, MainLocation, MainType FROM Main WHERE MainType= 'typeIWant' ";