經過對象直接增刪該查

@SpringBootTest

class SpringbootDemo2MybatisApplicationTests {

    @Autowired

    private UserDao userDao;

    @Test

    public void testFind(){

        List<User> userList = userDao.findAll();

        System.out.println(userList);

    }

    @Test

    public void testSelect01(){

        List<User> userList = userDao.selectList(null);

        System.out.println(userList);

    }

    /**

 * 業務: 查詢id=11的用戶信息   主鍵...

 */

    @Test

    public void testSelect02(){

        User user = userDao.selectById(11);

        System.out.println(user);

    }

    /**

 * 業務: 查詢name屬性爲"小喬"的數據

 * sql:  select * from user where name="小喬";

 * 對象的方式  >  sql方式

 */

    @Test

    public void testSelect03(){

        //條件構造器

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.eq("name", "小喬");

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 業務: 查詢name屬性爲"小喬"的數據 而且 age >=18歲

 * sql:  select * from user where name="小喬" and age>=18;

 *

 * 大於   >  gt| 小於 <  lt   |

 * 大於等於  >= ge  |  小於等於 le

 */

    @Test

    public void testSelect04(){

        //條件構造器

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.eq("name", "小喬")

                    .ge("age", 18);

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 業務: 查詢name中包含 "精"的用戶,而且sex爲女

 * 業務: 查詢name中包含 以精結尾的數據,而且sex爲女

 * sql:  select * from user where name like "%精%" and sex="女";

 */

    @Test

    public void testSelect05(){

        //條件構造器

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.likeLeft("name", "精")

                    .eq("sex", "女");

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 需求: 查詢user表中的數據 要求按照年齡降序排列,若是年齡相同按照id降序排列

 */

    @Test

    public void testSelect06(){

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.orderByDesc("age","id");

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 需求: 查詢name屬性爲null的數據.

 * where name is null

 */

    @Test

    public void testSelect07(){

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.isNull("name");

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 查詢name="小喬" age=17 性別=女的用戶

 * 若是傳遞的是對象.會根據對象中不爲null的屬性充當where條件.

 */

    @Test

    public void testSelect08(){

        User user = new User();

        user.setName("小喬").setAge(17).setSex("女");

        QueryWrapper<User> queryWrapper = new QueryWrapper<>(user);

        List<User> userList = userDao.selectList(queryWrapper);

        System.out.println(userList);

    }

    /**

 * 查詢id=1,3,5,10數據.

 * sql: select * from user where id in (1,3,5,10)

 */

    @Test

    public void testSelect09(){

        //轉化時,注意使用對象的類型

        Integer[] ids = {1,3,5,10};

        List<Integer> idList = Arrays.asList(ids);

        List<User> userList = userDao.selectBatchIds(idList);

        System.out.println(userList);

    }

    @Test

    public void testInsert(){

        User user = new User();

        user.setName("特朗普").setAge(70).setSex("男");

        userDao.insert(user);

    }

    /**

 * 刪除name=null的數據,或者name="特朗普"

 */

    @Test

    public void testDelete(){

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper.isNull("name")

                    .or()

                    .eq("name", "特朗普");

        userDao.delete(queryWrapper);

    }

    /**

 * 案例1: 將id=1的數據的年齡改成8000歲.

 * sql1:  update user set age=8000 where id=1;

 * 案例2: 要求將name="黑熊精" age=5500.

 * sql2:  update user set age=5500 where name="黑熊精";

 */

    @Test

    public void testUpdate(){

        User user = new User();

        user.setId(1);    //主鍵充當where條件

        user.setAge(8000);

        userDao.updateById(user);

        //參數說明  1.實體對象  封裝set條件的值

        //           2.更新條件構造器

        User temp = new User();

        temp.setAge(5500);

        UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();

        updateWrapper.eq("name", "黑熊精");

        userDao.update(temp,updateWrapper);

    }

}

2.pojo層實現實現實現實現實現
@Data
@TableName  //("user")      //1.將對象與表 進行一對一關聯
public class User implements Serializable {
    @TableId(type = IdType.AUTO)    //主鍵的信息  設定自增
    private Integer Id;
    //@TableField("name")     //若是字段名稱與屬性的名稱一致(包含駝峯規則),能夠省略不寫
    private String name;
    private Integer age;
    private String sex;
}

mapper層層層層層層層層層層層層層層層層層層層層層層層層層層層
public interface UserDao extends BaseMapper<User> {

//查詢user表的全部的記錄
@Select("select * from user")
List<User> findAll();

}
//mapperscan包名寫在mapper層
@SpringBootApplication
@MapperScan("com.jt.mapper")
public class SpringbootDemo3WebApplication {

public static void main(String[] args) {

SpringApplication.run(SpringbootDemo3WebApplication.class, args);

}

}