如何在where子句中使用查询中的变量的SQL UNION

Question

我试图从两个表中使用UNION检索数据，但不适用于我的情况。 我想这

$folq = $db->query("select id as pid,folder,name as catname,name,thumb,pathc from hollywood where id = ".$parentid, database::GET_ROW) UNION ("select id as pid,folder,name as catname,name,thumb,pathc from bollywood where id = ".$parentid, database::GET_ROW); 

但不是为我工作。请建议我如何实现这一点。

Answer 1

您需要一个查询字符串（而不是两个，而在第二个查询你不需要别名）

$folq = $db->query(" 
    select 
     id as pid 
     ,folder 
     ,name as catname 
     ,name 
     ,thumb 
     ,pathc 
    from hollywood 
    where id = ".$parentid . 
    " UNION 
    select 
     id 
     ,folder 
     ,name 
     ,name 
     ,thumb 
     ,pathc 
    from bollywood 
    where id = ". $parentid 

    , database::GET_ROW); 

Answer 2

我想在您的查询有语法错误，应该是这样的

$folq = $db->query("select id as pid,folder,name as catname,name,thumb,pathc from hollywood where id = ".$parentid . " UNION select id as pid,folder,name as catname,name,thumb,pathc from bollywood where id = ".$parentid, database::GET_ROW); 

Answer 3

请使用

 $folq = $this->db->query(" 
      select id as pid,folder,name as catname,name,thumb,pathc from hollywood where id = $parentid 
     UNION 
      select id as pid,folder,name as catname,name,thumb,pathc from bollywood where id = ".$parentid); 

Answer 4

这工作:)

  $folq = $db->query(" 
     select id as pid,folder,name as   catname,name,thumb,pathc from category where id   = $parentid 
      UNION 
      select id as pid,folder,name as   catname,name,thumb,pathc from punjabi where id   = ".$parentid, database::GET_ROW);