關(guān)鍵字：association 一對一映射（一個班級只有一個班主任）
|
1
2
3
4
5
6
7
8
9
10
11
|
<select id="getclass" parametertype="int" resultmap="classesresultmap"> select * from class c,teacher t where c.teacher_id=t.t_id and c.c_id=#{id} </select> <resultmap type="com.lcb.user.classes" id="classesresultmap"> <id property="id" column="c_id"/> <result property="name" column="c_name"/> <association property="teacher" javatype="com.lcb.user.teacher"> <id property="id" column="t_id"/> <result property="name" column="t_name"/> </association> </resultmap> |
關(guān)鍵字：collection 一對多映射（一個老師有多個學(xué)生）
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
|
<resultmap type="teacher" id="teachermaps"> <id column="id" property="id"/> <result column="name" property="name"/> <result column="class_name" property="classname"/> <collection property="students" oftype="student" select="getstudents" column="id"> </collection> </resultmap> <!-- 查詢所有的老師級各自的所有學(xué)生 --> <select id="getallteacher" parametertype="teacher" resultmap="teachermaps"> select t.id, t.name, t.class_name from teacher t </select> <select id="getstudents" parametertype="int" resulttype="student"> select s.id, s. name, s.class_name as classname from student s where teacher_id = #{id} </select> |
關(guān)鍵字：association 多對一映射（多個人屬于一個國家）
多對一相當(dāng)于一對多，也可以使用collection
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
|
<select id="selectcountry" resulttype="country"> select cid,cname from country where cid=#{ooo} </select> <resultmap type="people" id="peoplemapper2"> <id column="pid" property="pid"/> <result column="pname" property="pname"/> <association property="country" javatype="country" select="selectcountry" column="countryid" /> </resultmap> <select id="selectbyid2" resultmap="peoplemapper2"> select pid,pname,countryid from people where pid = #{xxx} </select> |
總結(jié)
以上所述是小編給大家介紹的mybatis 一對一、一對多和多對多查詢，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復(fù)大家的。在此也非常感謝大家對服務(wù)器之家網(wǎng)站的支持！
原文鏈接：https://blog.csdn.net/weixin_38048680/article/details/80307466
