Mybatis-Plus中的复杂条件查询_mybatis 复杂条件

wrapper介绍

Wrapper： 条件构造抽象类，最顶端父类
AbstractWrapper： 用于查询条件封装，生成 sql 的 where 条件
QueryWrapper： Entity 对象封装操作类，不是用lambda语法
UpdateWrapper： Update 条件封装，用于Entity对象更新操作
AbstractLambdaWrapper： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。
LambdaQueryWrapper：用于Lambda语法使用的查询Wrapper
LambdaUpdateWrapper： Lambda 更新封装Wrapper

具体步骤

• 创建QueryWrapper对象
• 通过QueryWrapper设置条件

具体实现

在MyBatis-Plus入门案例基础上进行修改。

    @Test
    void testCondQuery() {
        //创建QueryWrapper对象
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        //通过QueryWrapper设置条件
        //ge、gt、le、lt
        //查询 age >= 30 的记录
//        wrapper.ge("age",40);

        //eq、ne
//        wrapper.eq("name","pdd");

        //between
//        wrapper.between("age",100,200);

        //like
//        wrapper.like("name","k");

        //orderByDesc
//        wrapper.orderByDesc("id");

        //last
//        wrapper.last("limit 1");

        //查询指定的列
        wrapper.select("id","name");

        List<User> users = userMapper.selectList(wrapper);
        System.out.println(users);
    }
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更多例子

ge、gt、le、lt、isNull、isNotNull

    @Test
    public void testDelete() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper
                .isNull("name")
                .ge("age", 12)
                .isNotNull("email");
        int result = userMapper.delete(queryWrapper);
        System.out.println("delete return count = " + result);
    }
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UPDATE user SET deleted=1 WHERE deleted=0 AND name IS NULL AND age >= ? AND email IS NOT NULL
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eq、ne

    @Test
    public void testSelectOne() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("name", "Tom");
        User user = userMapper.selectOne(queryWrapper);
        System.out.println(user);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name = ?
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between、notBetween

    @Test
    public void testSelectCount() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.between("age", 20, 30);
        Integer count = userMapper.selectCount(queryWrapper);
        System.out.println(count);
    }
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SELECT COUNT(1) FROM user WHERE deleted=0 AND age BETWEEN ? AND ?
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allEq

    @Test
    public void testSelectList() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        Map<String, Object> map = new HashMap<>();
        map.put("id", 2);
        map.put("name", "Jack");
        map.put("age", 20);
        queryWrapper.allEq(map);
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name = ? AND id = ? AND age = ?
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like、notLike、likeLeft、likeRight

    @Test
    public void testSelectMaps() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.notLike("name", "e")
                .likeRight("email", "t");
        List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
        maps.forEach(System.out::println);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name NOT LIKE ? AND email LIKE ?
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in、notIn、inSql、notinSql、exists、notExists

    @Test
    public void testSelectObjs() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        //queryWrapper.in("id", 1, 2, 3);
        queryWrapper.inSql("id", "select id from user where id < 3");
        List<Object> objects = userMapper.selectObjs(queryWrapper);//返回值是Object列表
        objects.forEach(System.out::println);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND id IN (select id from user where id < 3)
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or、and

不调用or则默认为使用 and 连

    @Test
    public void testUpdate1() {
        //修改值
        User user = new User();
        user.setAge(99);
        user.setName("Andy");
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
                .like("name", "h")
                .or()
                .between("age", 20, 30);
        int result = userMapper.update(user, userUpdateWrapper);
        System.out.println(result);
    }
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UPDATE user SET name=?, age=?, update_time=? WHERE deleted=0 AND name LIKE ? OR age BETWEEN ? AND ?
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嵌套or、嵌套and

    @Test
    public void testUpdate2() {
        //修改值
        User user = new User();
        user.setAge(99);
        user.setName("Andy");
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
                .like("name", "h")
                .or(i -> i.eq("name", "李白").ne("age", 20));
        int result = userMapper.update(user, userUpdateWrapper);
        System.out.println(result);
    }
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UPDATE user SET name=?, age=?, update_time=? WHERE deleted=0 AND name LIKE ? OR ( name = ? AND age <> ? )
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orderBy、orderByDesc、orderByAsc

    @Test
    public void testSelectListOrderBy() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("id");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 ORDER BY id DESC
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last

    @Test
    public void testSelectListLast() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.last("limit 1");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }
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SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 limit 1
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指定要查询的列

    @Test
    public void testSelectListColumn() {
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.select("id", "name", "age");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }
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SELECT id,name,age FROM user WHERE deleted=0
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set、setSql

    @Test
    public void testUpdateSet() {
        //修改值
        User user = new User();
        user.setAge(99);
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
                .like("name", "h")
                .set("name", "老李头")//除了可以查询还可以使用set设置修改的字段
                .setSql(" email = '123@qq.com'");//可以有子查询
        int result = userMapper.update(user, userUpdateWrapper);
    }
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UPDATE user SET age=?, update_time=?, name=?, email = '123@qq.com' WHERE deleted=0 AND name LIKE ?
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