UNION与带有大WHERE子句的两个查询

我有两个几乎相同的查询-一个连接表gz_life_groups和gz_life_groups2，另一个连接gz_life_floaters和gz_life_floaters2。我想使用UNION将两个查询合并到一个查询中，但是我还没有跳过所有的麻烦。

表格的简要说明：想象一下导航到URL MySite / life / ursus-maritimus。Ursus-maritimus与数据库表字段Taxon中的值匹配。因此，如果已将Ursus maritimus（北极熊）放在名为“ White Mammals”的组中，则它将与表gz_life_groups中标题（“ White Mammals”）和URL（“ white-mammals”）中的值匹配。链接字段仅包含指向相关页面的链接。

查询1

$Groups = $pdo->prepare("SELECT G2.URL, G2.Taxon, G1.URL, G1.Title, G1.Links
 FROM gz_life_groups2 AS G2
 LEFT JOIN gz_life_groups G1 ON G1.URL = G2.URL
 WHERE Taxon = :Kingdom AND G2.Live = '1'
 OR Taxon = :Phylum AND G2.Live = '1'
 OR Taxon = :Class AND G2.Live = '1'
 OR Taxon = :Order AND G2.Live = '1'
 OR Taxon = :Family AND G2.Live = '1'
 OR Taxon = :Genus AND G2.Live = '1'
 OR Taxon = :MyURL AND G2.Live = '1'
 GROUP BY G1.URL
 Order By G2.N");
$Groups->execute(array(
 'Kingdom'=>$Kingdom,
 'Phylum'=>$Phylum,
 'Class'=>$Class,
 'Order'=>$Order,
 'Family'=>$Family,
 'Genus'=>$Genus,
 'MyURL'=>$MyURL
));

查询2

$Names = $pdo->prepare("SELECT F2.URL, F2.Taxon, F1.URL, F1.Name, F1.Parent
 FROM gz_life_floaters2 AS F2
 LEFT JOIN gz_life_floaters F1 ON F1.URL = F2.URL
 WHERE Taxon = :Kingdom AND F2.Live = '1'
 OR Taxon = :Phylum AND F2.Live = '1'
 OR Taxon = :Class AND F2.Live = '1'
 OR Taxon = :Order AND F2.Live = '1'
 OR Taxon = :Family AND F2.Live = '1'
 OR Taxon = :Genus AND F2.Live = '1'
 OR Taxon = :MyURL AND F2.Live = '1'
 GROUP BY F1.URL
 Order By F2.N");
$Names->execute(array(
 'Kingdom'=>$Kingdom,
 'Phylum'=>$Phylum,
 'Class'=>$Class,
 'Order'=>$Order,
 'Family'=>$Family,
 'Genus'=>$Genus,
 'MyURL'=>$MyURL
));

就我对UNION的有限了解带给我的。我不知道如何添加联接或WHERE子句...

$stm = $pdo->prepare("SELECT *
 FROM (
 SELECT G2.URL, G2.Taxon, G1.URL, G1.Title, NULL AS Parent, G1.Links
 FROM gz_life_groups2 AS G2
 UNION ALL 
 SELECT F2.URL, F2.Taxon, F1.URL, F1.Name AS Title, F1.Parent, NULL AS Links
 FROM gz_life_floaters2 AS F2
) AS Combined
 WHERE Combined.URL LIKE :MyURL");
$stm->execute(array(
'MyURL'=>$MyURL
));