MybatisPlus結(jié)合groupby實現(xiàn)分組和sum求和的步驟

更新時間：2023年12月11日 09:53:42 作者：知識淺談

這篇文章主要介紹了MybatisPlus結(jié)合groupby實現(xiàn)分組和sum求和的步驟,這次使用的是LambdaQueryWrapper,使用QueryWrapper相對來說簡單點就不寫了,本文分步驟給大家介紹的非常詳細,感興趣的朋友一起看看吧

?MybatisPlus結(jié)合groupby實現(xiàn)分組和sum求和

這次使用的是LambdaQueryWrapper，使用QueryWrapper相對來說簡單點就不寫了

??實現(xiàn)GroupBy分組

第一步: 實體類中新增一個字段count

@TableName(value ="user")
@Data
public class User implements Serializable {
    @TableId(type = IdType.AUTO)
    private Integer id;
    @TableField(value = "name")
    private String name;
    @TableField(value = "age")
    private Integer age;
    @TableField(value = "state")
    private String state;
    @TableField(exist = false)
    private static final long serialVersionUID = 1L;
	//這個地方
    @TableField(value = "count(*)",insertStrategy = FieldStrategy.NEVER,updateStrategy = FieldStrategy.NEVER)
    private  Integer count;
}

第二步：查詢接口中修改

   @GetMapping("/count")
   public List<User> count(){
       new QueryWrapper<>()
       LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
       queryWrapper.select(User::getState,User::getCount);
       queryWrapper.groupBy(User::getState);
       List<User> list = userService.list(queryWrapper);
       return list;
   }

返回的結(jié)果

[
{
"id": null,
"name": null,
"age": null,
"state": "1",
"count": 3
},
{
"id": null,
"name": null,
"age": null,
"state": "2",
"count": 2
}
]

??實現(xiàn)GroupBy分組之后再sum求和

第一步: 實體類中新增一個字段count

@TableName(value ="user")
@Data
public class User implements Serializable {
    @TableId(type = IdType.AUTO)
    private Integer id;
    @TableField(value = "name")
    private String name;
    @TableField(value = "age")
    private Integer age;
    @TableField(value = "state")
    private String state;
    @TableField(exist = false)
    private static final long serialVersionUID = 1L;
    @TableField(value = "count(*)",insertStrategy = FieldStrategy.NEVER,updateStrategy = FieldStrategy.NEVER)
    private  Integer count;
	//這個地方
    @TableField(value = "sum(age)",insertStrategy = FieldStrategy.NEVER,updateStrategy = FieldStrategy.NEVER)
    private  Integer ages;
}

第二步：查詢接口中修改

   @GetMapping("/count")
   public List<User> count(){
       new QueryWrapper<>()
       LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
       //這個地方新增了一個字段
       queryWrapper.select(User::getState,User::getCount,User::getAges);
       queryWrapper.groupBy(User::getState);
       List<User> list = userService.list(queryWrapper);
       return list;
   }

返回的結(jié)果

[
{
"id": null,
"name": null,
"age": null,
"state": "1",
"count": 3,
"ages": 6
},
{
"id": null,
"name": null,
"age": null,
"state": "2",
"count": 2,
"ages": 9
}
]