Sql server 2008 在sql server中选择“使用多个表查询”

嘿，伙计们， 我的sql server数据库中有3个表。 1.crossarticle\u文章具有字段：Title 2.blogs\u条目包含字段：title 3.论坛和你的帖子。has字段：subject

现在我想做的是，我在我的网站上搜索，当用户在搜索框中输入任何关键字并点击按钮时，它应该在所有这些表中搜索标题，并返回单个结果集

如何实现这一点，我正在使用sql server 2008

A将返回唯一的结果，而A将返回所有结果，包括重复的结果

SELECT Title
FROM crossarticle_article
WHERE Title = @Title

UNION

SELECT title
FROM blogs_entries
WHERE title = @Title

UNION

SELECT subject
FROM forums_posts
WHERE subject = @Title

SELECT Title
FROM crossarticle_article
WHERE Title = '%term%'
UNION
SELECT Title
FROM blogs_entries
WHERE Title = '%term%'
UNION
SELECT subject AS Title
FROM forums_posts
WHERE Title = '%term%'

比如：

SELECT "article"                  AS type
     , crossarticle_article.id    AS id
     , crossarticle_article.Title AS title_subject
FROM crossarticle_article 
WHERE Title LIKE "%userinput%"

UNION ALL

SELECT "blog entry"               AS type
     , blogs_entries.id           AS id     
     , blogs_entries.title        AS title_subject
FROM blogs_entries
WHERE title LIKE "%userinput%"

UNION ALL 

SELECT "forum post"               AS type
     , forums_posts.id            AS id
     , forums_posts.subject       AS title_subject
FROM forums_posts
WHERE subject LIKE "%userinput%"

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编写3个查询并将它们与

UNION

组合。感谢您解释

UNION

和

UNION ALL

之间的区别