【Mybatis3】—— 使用collection处理一对多映射

最新推荐文章于 2025-07-10 20:20:31 发布

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最新推荐文章于 2025-07-10 20:20:31 发布 · 4.3k 阅读

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文章标签：

#mybatis3 #collection

本文介绍了如何在Mybatis3中处理一对多映射，通过创建数据库表、POJO对象、接口和XML文件，展示了Controller测试及结果。同时，文章详细讨论了在一对多映射中遇到的两个问题：相同字段导致的数据覆盖和查询结果数量限制，并提供了解决方案，即为相同字段设置别名以避免冲突。

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1. 创建数据库表

tb_classroom 帖子表

-- Table: public.tb_classroom

-- DROP TABLE public.tb_classroom;

CREATE TABLE public.tb_classroom
(
    id integer NOT NULL DEFAULT nextval('tb_classroom_id_seq'::regclass),
    classroom_no character varying(20) COLLATE pg_catalog."default" NOT NULL,
    name character varying(20) COLLATE pg_catalog."default" NOT NULL,
    CONSTRAINT tb_classroom_pkey PRIMARY KEY (id)
)
WITH (
    OIDS = FALSE
)
TABLESPACE pg_default;

ALTER TABLE public.tb_classroom
    OWNER to postgres;
COMMENT ON TABLE public.tb_classroom
    IS '班级信息表';

-- Index: unique_index_on_classroom_no

-- DROP INDEX public.unique_index_on_classroom_no;

CREATE UNIQUE INDEX unique_index_on_classroom_no
    ON public.tb_classroom USING btree
    (classroom_no COLLATE pg_catalog."default")
    TABLESPACE pg_default;

插入数据:

INSERT INTO "public"."tb_classroom" VALUES ('1', 'C003001', '三年一班');
INSERT INTO "public"."tb_classroom" VALUES ('3', 'C003002', '三年二班');

tb_student 用户表

-- Table: public.tb_student

-- DROP TABLE public.tb_student;

CREATE TABLE public.tb_student
(
    id integer NOT NULL DEFAULT nextval('tb_student_id_seq'::regclass),
    student_no character varying(20) COLLATE pg_catalog."default" NOT NULL,
    name character varying(20) COLLATE pg_catalog."default" NOT NULL,
    age smallint NOT NULL,
    score real NOT NULL,
    classroom_no character varying(20) COLLATE pg_catalog."default" NOT NULL,
    CONSTRAINT tb_student_pkey PRIMARY KEY (id)
)
WITH (
    OIDS = FALSE
)
TABLESPACE pg_default;

ALTER TABLE public.tb_student
    OWNER to postgres;
COMMENT ON TABLE public.tb_student
    IS '学生信息表';

-- Index: unique_index_on_student_no

-- DROP INDEX public.unique_index_on_student_no;

CREATE UNIQUE INDEX unique_index_on_student_no
    ON public.tb_student USING btree
    (student_no COLLATE pg_catalog."default")
    TABLESPACE pg_default;

插入数据:

INSERT INTO "public"."tb_student" VALUES ('1', 'S315060012', '小明', '25', '88.5', 'C003001');
INSERT INTO "public"."tb_student" VALUES ('2', 'S315060039', '小黄', '24', '92.5', 'C003001');
INSERT INTO "public"."tb_student" VALUES ('3', 'S315060011',