使用mybatis 实现量表关联并且统计数据量的步骤和代码

<dependencies>
    <!-- Spring Boot 基础 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- MyBatis 整合 Spring Boot -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>3.0.2</version>
    </dependency>
    <!-- MySQL 驱动 -->
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <scope>runtime</scope>
    </dependency>
    <!-- EasyExcel 用于生成 Excel -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>easyexcel</artifactId>
        <version>3.3.2</version>
    </dependency>
    <!-- Lombok 简化代码 -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <!-- 测试依赖 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test_db?useSSL=false&serverTimezone=UTC&characterEncoding=utf8
    username: 你的数据库用户名
    password: 你的数据库密码
    driver-class-name: com.mysql.cj.jdbc.Driver
mybatis:
  mapper-locations: classpath:mapper/*.xml

package com.example.entity;
import lombok.Data;
@Data
public class A {
    private String tableName;
    private String count;
    private String id;
}

package com.example.entity;
import lombok.Data;
@Data
public class B {
    private String tableNameDcif;
    private String tableNameSou;
    private String id;
}

package com.example.vo;
import com.alibaba.excel.annotation.ExcelProperty;
import lombok.Data;
@Data
public class ExcelVO {
    @ExcelProperty("table_name_dcif")
    private String tableNameDcif;
    @ExcelProperty("count（dcif开头表数量）")
    private String dcifCount;
    @ExcelProperty("table_name_sou")
    private String tableNameSou;
    @ExcelProperty("count（sou_开头表数量）")
    private String souCount;
}

package com.example.mapper;
import com.example.entity.A;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import java.util.List;
@Mapper
public interface AMapper {
    @Select("SELECT table_name, `count` FROM a WHERE table_name LIKE 'dcif_%'")
    List<A> selectDcifTables();
    @Select("SELECT `count` FROM a WHERE table_name = #{tableName}")
    String selectCountByTableName(String tableName);
}

package com.example.mapper;
import com.example.entity.B;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import java.util.List;
@Mapper
public interface BMapper {
    @Select("SELECT table_name_sou FROM b WHERE table_name_dcif = #{tableNameDcif}")
    List<String> selectSouTablesByDcif(String tableNameDcif);
}

package com.example.service;
import com.alibaba.excel.EasyExcel;
import com.example.entity.A;
import com.example.mapper.AMapper;
import com.example.mapper.BMapper;
import com.example.vo.ExcelVO;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import java.util.ArrayList;
import java.util.List;
@Service
@RequiredArgsConstructor
public class ExcelService {
    private final AMapper aMapper;
    private final BMapper bMapper;
    public void exportExcel(String filePath) {
        // 1. 查询所有 dcif 开头的表及对应 count
        List<A> dcifTables = aMapper.selectDcifTables();
        // 2. 组装 Excel 数据
        List<ExcelVO> excelData = new ArrayList<>();
        for (A dcifTable : dcifTables) {
            String dcifTableName = dcifTable.getTableName();
            String dcifCount = dcifTable.getCount();
            // 查询该 dcif 表对应的所有 sou_ 表
            List<String> souTables = bMapper.selectSouTablesByDcif(dcifTableName);
            for (String souTable : souTables) {
                // 查询 sou_ 表的 count
                String souCount = aMapper.selectCountByTableName(souTable);
                ExcelVO vo = new ExcelVO();
                vo.setTableNameDcif(dcifTableName);
                vo.setDcifCount(dcifCount);
                vo.setTableNameSou(souTable);
                vo.setSouCount(souCount);
                excelData.add(vo);
            }
        }
        // 3. 导出 Excel
        EasyExcel.write(filePath, ExcelVO.class)
               .sheet("数据统计")
               .doWrite(excelData);
    }
}

package com.example.controller;
import com.example.service.ExcelService;
import lombok.RequiredArgsConstructor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/excel")
@RequiredArgsConstructor
public class ExcelController {
    private final ExcelService excelService;
    @GetMapping("/export")
    public String exportExcel() {
        String filePath = "D:/data_statistics.xlsx"; // 导出文件路径
        excelService.exportExcel(filePath);
        return "Excel 导出成功，路径：" + filePath;
    }
}

package com.example.service;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import javax.annotation.Resource;
@SpringBootTest
class ExcelServiceTest {
    @Resource
    private ExcelService excelService;
    @Test
    void exportExcel() {
        String filePath = "D:/data_statistics.xlsx";
        excelService.exportExcel(filePath);
        System.out.println("Excel 导出成功，路径：" + filePath);
    }
}