Mybatis高级结果映射
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2016-08-10
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Mybatis 高级结果映射
MyBatis 的创建基于这样一个思想：数据库并不是您想怎样就怎样的。虽然我们希望所有
的数据库遵守第三范式或 BCNF（修正的第三范式），但它们不是。如果有一个数据库能
够完美映射到所有应用程序，也将是非常棒的，但也没有。结果集映射就是 MyBatis 为解
决这些问题而提供的解决方案。例如，我们如何映射下面这条语句？
[sql] view plain copy
1 <select id="selectBlogDetails" parameterType="int"
resultMap="detailedBlogResultMap">
2 select
3 B.id as blog_id,
4 B.title as blog_title,
5 B.author_id as blog_author_id,
6 A.id as author_id,
7 A.username as author_username,
8 A.password as author_password,
9 A.email as author_email,
10 A.bio as author_bio,
11 A.favourite_section as author_favourite_section,
12 P.id as post_id,
13 P.blog_id as post_blog_id,
14 P.author_id as post_author_id,
15 P.created_on as post_created_on,
16 P.section as post_section,
17 P.subject as post_subject,
18 P.draft as draft,
19 P.body as post_body,
20 C.id as comment_id,
21 C.post_id as comment_post_id,
22 C.name as comment_name,
23 C.comment as comment_text,
24 T.id as tag_id,
25 T.name as tag_name
26 from Blog B
27 left outer join Author A on B.author_id = A.id
28 left outer join Post P on B.id = P.blog_id
29 left outer join Comment C on P.id = C.post_id
30 left outer join Post_Tag PT on PT.post_id = P.id
31 left outer join Tag T on PT.tag_id = T.id
32 where B.id = #{id}
33 </select>
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