Mybatis--其他查询操作和数据库连接池（下下）

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序

准备工作：

mysql数据库和表的信息更新：

DROP TABLE IF EXISTS articleinfo;CREATE TABLE articleinfo (id INT PRIMARY KEY auto_increment,title VARCHAR ( 100 ) NOT NULL,content TEXT NOT NULL,uid INT NOT NULL,delete_flag TINYINT ( 4 ) DEFAULT 0 COMMENT '0-正常, 1-删除',create_time DATETIME DEFAULT now(),update_time DATETIME DEFAULT now()
) DEFAULT charset 'utf8mb4';-- 插入测试数据
INSERT INTO articleinfo ( title, content, uid ) VALUES ( '十日游戏', 'snh48群像', 1 );

对应实体类model：

package com.example.zxslzw_mybaties.model;import lombok.Data;import java.util.Date;@Data
public class ArticleInfo {private Integer id;private String title;private String content;private Integer uid;private Integer deleteFlag;;private Date createTime;private Date updateTime;//用户相关的信息private String username;private Integer gender;
}

1. 多表查询

多表查询和单表查询差不多，只是SQL代码不同，下面是xml的配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.zxslzw_mybaties.mapper.ArticleInfoMapper"><select id="selectArticleAndUserById" resultType="com.example.zxslzw_mybaties.model.ArticleInfo">select ta.*, tb.username, tb.gender from articleinfo taleft join userinfo tbon ta.uid = tb.idwhere ta.id = #{id}</select>
</mapper>

ArticleInfoMapper接口代码如下：

package com.example.zxslzw_mybaties.mapper;import com.example.zxslzw_mybaties.model.ArticleInfo;
import org.apache.ibatis.annotations.Mapper;import java.util.List;@Mapper
public interface ArticleInfoMapper {List<ArticleInfo> selectArticleAndUserById(Integer id);
}

测试类代码如下：

package com.example.zxslzw_mybaties.mapper;import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import static org.junit.jupiter.api.Assertions.*;
@SpringBootTest
class ArticleInfoMapperTest {@Autowiredprivate ArticleInfoMapper articleInfoMapper;@Testvoid selectArticleAndUserById() {System.out.println(articleInfoMapper.selectArticleAndUserById(1));}
}

articleInfo和userinfo表如下：