MyBatis-Plus多表联查的实现方法(动态查询和静态查询)

2024-07-28 17:36:18

建库建表

DROP DATABASE IF EXISTS mp;
CREATE DATABASE mp DEFAULT CHARACTER SET utf8;
USE mp;

DROP TABLE IF EXISTS `t_user`;
DROP TABLE IF EXISTS `t_blog`;
SET NAMES utf8mb4;
CREATE TABLE `t_user`
(
    `id`              BIGINT(0) NOT NULL AUTO_INCREMENT,
    `user_name`       VARCHAR(64) NOT NULL COMMENT '用户名（不能重复）',
    `nick_name`       VARCHAR(64) NOT NULL COMMENT '昵称（可以重复）',
    `email`           VARCHAR(64) COMMENT '邮箱',
    `create_time`  DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    `update_time` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '修改时间',
    `deleted_flag` BIGINT(0) NOT NULL DEFAULT 0 COMMENT '0：未删除 其他：已删除',
    PRIMARY KEY (`id`) USING BTREE,
    UNIQUE KEY `index_user_name_deleted_flag`(`user_name`, `deleted_flag`),
    KEY `index_create_time`(`create_time`)
) ENGINE = InnoDB COMMENT = '用户';
CREATE TABLE `t_blog`
    `id`           BIGINT(0) NOT NULL AUTO_INCREMENT,
    `user_id`      BIGINT(0) NOT NULL,
    `user_name`    VARCHAR(64) NOT NULL,
    `title`        VARCHAR(256) CHARACTER SET utf8mb4 NOT NULL COMMENT '标题',
    `description`  VARCHAR(256) CHARACTER SET utf8mb4 NOT NULL COMMENT '摘要',
    `content`      LONGTEXT CHARACTER SET utf8mb4 NOT NULL COMMENT '内容',
    KEY `index_user_id`(`user_id`),
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COMMENT = '博客';
INSERT INTO `t_user` VALUES (1, 'knife', '刀刃', 'abc@qq.com', '2021-01-23 09:33:36', '2021-01-23 09:33:36', 0);
INSERT INTO `t_user` VALUES (2, 'sky', '天蓝', '123@qq.com', '2021-01-24 18:12:21', '2021-01-24 18:12:21', 0);
INSERT INTO `t_blog` VALUES (1, 1, 'knife', 'Java中枚举的用法',
                             '本文介绍Java的枚举类的使用',
                             '2021-01-23 11:33:36', '2021-01-23 11:33:36', 0);
INSERT INTO `t_blog` VALUES (2, 1, 'knife', 'Java中泛型的用法',
                             '本文介绍Java的泛型的使用。',
                             '2021-01-28 23:37:37', '2021-01-28 23:37:37', 0);
INSERT INTO `t_blog` VALUES (3, 1, 'knife', 'Java的HashMap的原理',
                             '本文介绍Java的HashMap的原理。',
                             '2021-05-28 09:06:06', '2021-05-28 09:06:06', 0);
INSERT INTO `t_blog` VALUES (4, 1, 'knife', 'Java中BigDecimal的用法',
                             '本文介绍Java的BigDecimal的使用。',
                             '2021-06-24 20:36:54', '2021-06-24 20:36:54', 0);
INSERT INTO `t_blog` VALUES (5, 1, 'knife', 'Java中反射的用法',
                             '本文介绍Java的反射的使用。',
                             '2021-10-28 22:24:18', '2021-10-28 22:24:18', 0);
INSERT INTO `t_blog` VALUES (6, 2, 'sky', 'Vue-cli的使用',
                             'Vue-cli是Vue的一个脚手架工具',
                             'Vue-cli可以用来创建vue项目',
                             '2021-02-23 11:34:36', '2021-02-25 14:33:36', 0);
INSERT INTO `t_blog` VALUES (7, 2, 'sky', 'Vuex的用法',
                             'Vuex是vue用于共享变量的插件',
                             '一般使用vuex来共享变量',
                             '2021-03-28 23:37:37', '2021-03-28 23:37:37', 0);

依赖

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>MyBatis-Plus_Multiple</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>MyBatis-Plus_Multiple</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.12.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>3.0.3</version>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <!-- 指定maven编译的jdk版本。若不指定,maven3默认用jdk 1.5 maven2默认用jdk1.3 -->
                <configuration>
                    <source>8</source>
                    <target>8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

配置

application.yml

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/mp?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf8&useSSL=false
    password: 222333
    username: root

#mybatis-plus配置控制台打印完整带参数SQL语句
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

MyBatis-Plus分页插件配置

package com.example.demo.config;

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
@Configuration
public class MyBatisPlusConfig {
    /**
     * 分页插件
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

代码

package com.example.demo.business.blog.vo;

import lombok.Data;
import java.time.LocalDateTime;
@Data
public class BlogVO {
    private Long id;
    private Long userId;
    private String userName;
    /**
     * 标题
     */
    private String title;
     * 摘要
    private String description;
     * 内容
    private String content;
     * 创建时间
    private LocalDateTime createTime;
     * 修改时间
    private LocalDateTime updateTime;
     * 昵称（这个是t_user的字段）
    private String nickName;
}

Mapper

package com.example.demo.business.blog.mapper;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.example.demo.business.blog.entity.Blog;
import com.example.demo.business.blog.vo.BlogVO;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface BlogMapper extends BaseMapper<Blog> {
    /**
     * 静态查询
     */
    @Select("SELECT t_user.user_name " +
            " FROM t_blog, t_user " +
            " WHERE t_blog.id = #{id} " +
            "     AND t_blog.user_id = t_user.id")
    String findUserNameByBlogId(@Param("id") Long id);
     * 动态查询
    @Select("SELECT * " +
            " ${ew.customSqlSegment} ")
    IPage<BlogVO> findBlog(IPage<BlogVO> page, @Param("ew") Wrapper wrapper);
}

Controller

package com.example.demo.business.blog.controller;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.demo.business.blog.mapper.BlogMapper;
import com.example.demo.business.blog.vo.BlogVO;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@Api(tags = "自定义SQL")
@RestController
@RequestMapping("/blog")
public class BlogController {
    @Autowired
    private BlogMapper blogMapper;
    @ApiOperation("静态查询")
    @GetMapping("staticQuery")
    public String staticQuery() {
        return blogMapper.findUserNameByBlogId(1L);
    }
    @ApiOperation("动态查询")
    @GetMapping("dynamicQuery")
    public IPage<BlogVO> dynamicQuery(Page<BlogVO> page, String nickName, String title) {
        QueryWrapper<BlogVO> queryWrapper = new QueryWrapper<>();
        queryWrapper.like(StringUtils.hasText(nickName), "t_user.nick_name", nickName);
        queryWrapper.like(StringUtils.hasText(title), "t_blog.title", title);
        queryWrapper.eq("t_blog.deleted_flag", 0);
        queryWrapper.eq("t_user.deleted_flag", 0);
        queryWrapper.apply("t_blog.user_id = t_user.id");
        return blogMapper.findBlog(page, queryWrapper);
}

测试

访问knife4j页面：http://localhost:8080/doc.html

1.静态查询

2.动态查询

1.不传条件

结果：（可以查到所有数据）

后端输出

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@60bbb9ec] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1853643659 wrapping com.mysql.cj.jdbc.ConnectionImpl@6a43d29c] will not be managed by Spring
==> Preparing: SELECT COUNT(*) AS total FROM t_blog, t_user WHERE (t_blog.deleted_flag = ? AND t_user.deleted_flag = ? AND t_blog.user_id = t_user.id)
==> Parameters: 0(Integer), 0(Integer)
<== Columns: total
<== Row: 7
<== Total: 1
==> Preparing: SELECT * FROM t_blog, t_user WHERE (t_blog.deleted_flag = ? AND t_user.deleted_flag = ? AND t_blog.user_id = t_user.id) LIMIT ?
==> Parameters: 0(Integer), 0(Integer), 10(Long)
<== Columns: id, user_id, user_name, title, description, content, create_time, update_time, deleted_flag, id, user_name, nick_name, email, create_time, update_time, deleted_flag
<== Row: 1, 1, knife, Java中枚举的用法, 本文介绍Java的枚举类的使用, <<BLOB>>, 2021-01-23 11:33:36, 2021-01-23 11:33:36, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 2, 1, knife, Java中泛型的用法, 本文介绍Java的泛型的使用。, <<BLOB>>, 2021-01-28 23:37:37, 2021-01-28 23:37:37, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 3, 1, knife, Java的HashMap的原理, 本文介绍Java的HashMap的原理。, <<BLOB>>, 2021-05-28 09:06:06, 2021-05-28 09:06:06, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 4, 1, knife, Java中BigDecimal的用法, 本文介绍Java的BigDecimal的使用。, <<BLOB>>, 2021-06-24 20:36:54, 2021-06-24 20:36:54, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 5, 1, knife, Java中反射的用法, 本文介绍Java的反射的使用。, <<BLOB>>, 2021-10-28 22:24:18, 2021-10-28 22:24:18, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 6, 2, sky, Vue-cli的使用, Vue-cli是Vue的一个脚手架工具, <<BLOB>>, 2021-02-23 11:34:36, 2021-02-25 14:33:36, 0, 2, sky, 天蓝, 123@qq.com, 2021-01-24 18:12:21, 2021-01-24 18:12:21, 0
<== Row: 7, 2, sky, Vuex的用法, Vuex是vue用于共享变量的插件, <<BLOB>>, 2021-03-28 23:37:37, 2021-03-28 23:37:37, 0, 2, sky, 天蓝, 123@qq.com, 2021-01-24 18:12:21, 2021-01-24 18:12:21, 0
<== Total: 7
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@60bbb9ec]

2.传条件

只传：nickName：刀

结果

后端结果

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@30026aab] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@2127441980 wrapping com.mysql.cj.jdbc.ConnectionImpl@6a43d29c] will not be managed by Spring
==> Preparing: SELECT COUNT(*) AS total FROM t_blog, t_user WHERE (t_user.nick_name LIKE ? AND t_blog.deleted_flag = ? AND t_user.deleted_flag = ? AND t_blog.user_id = t_user.id)
==> Parameters: %刀%(String), 0(Integer), 0(Integer)
<== Columns: total
<== Row: 5
<== Total: 1
==> Preparing: SELECT * FROM t_blog, t_user WHERE (t_user.nick_name LIKE ? AND t_blog.deleted_flag = ? AND t_user.deleted_flag = ? AND t_blog.user_id = t_user.id) LIMIT ?
==> Parameters: %刀%(String), 0(Integer), 0(Integer), 10(Long)
<== Columns: id, user_id, user_name, title, description, content, create_time, update_time, deleted_flag, id, user_name, nick_name, email, create_time, update_time, deleted_flag
<== Row: 1, 1, knife, Java中枚举的用法, 本文介绍Java的枚举类的使用, <<BLOB>>, 2021-01-23 11:33:36, 2021-01-23 11:33:36, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 2, 1, knife, Java中泛型的用法, 本文介绍Java的泛型的使用。, <<BLOB>>, 2021-01-28 23:37:37, 2021-01-28 23:37:37, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 3, 1, knife, Java的HashMap的原理, 本文介绍Java的HashMap的原理。, <<BLOB>>, 2021-05-28 09:06:06, 2021-05-28 09:06:06, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 4, 1, knife, Java中BigDecimal的用法, 本文介绍Java的BigDecimal的使用。, <<BLOB>>, 2021-06-24 20:36:54, 2021-06-24 20:36:54, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Row: 5, 1, knife, Java中反射的用法, 本文介绍Java的反射的使用。, <<BLOB>>, 2021-10-28 22:24:18, 2021-10-28 22:24:18, 0, 1, knife, 刀刃, abc@qq.com, 2021-01-23 09:33:36, 2021-01-23 09:33:36, 0
<== Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@30026aab]

到此这篇关于MyBatis-Plus多表联查(动态查询)的文章就介绍到这了,更多相关MyBatis-Plus多表联查内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！

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