查询帮助? MySQL,LEFT JOIN,GROUP BY,缺少数据

如何解决查询帮助? MySQL,LEFT JOIN,GROUP BY,缺少数据

| 如何更改此查询,以使其在添加2011-01-02行后​​仍显示0个在2011-01-01收到的flotsam?
mysql> SELECT * FROM Items;
+---------+
| Name    |
+---------+
| widgets | 
| things  | 
| stuff   | 
| flotsam | 
| jetsam  | 
+---------+

mysql> SELECT * FROM Received;
+---------+---------------+-------------+----------+
| Name    | invoiceNumber | invoiceDate | Quantity |
+---------+---------------+-------------+----------+
| widgets |             1 | 2011-01-01  |        1 | 
| widgets |             2 | 2011-01-01  |        2 | 
| things  |             3 | 2011-01-01  |        3 | 
| things  |             4 | 2011-01-01  |        4 | 
| stuff   |             5 | 2011-01-01  |        5 | 
| jetsam  |             7 | 2011-01-01  |        7 | 
+---------+---------------+-------------+----------+

mysql> SELECT Name,IFNULL(SUM(Quantity),0)
    -> FROM Items AS I
    -> LEFT JOIN Received AS R
    -> USING (Name)
    -> WHERE invoiceDate=\'2011-01-01\' OR invoiceDate IS NULL
    -> GROUP BY Name;
+---------+-------------------------+
| Name    | IFNULL(SUM(Quantity),0) |
+---------+-------------------------+
| flotsam |                       0 | 
| jetsam  |                       7 | 
| stuff   |                       5 | 
| things  |                       7 | 
| widgets |                       3 | 
+---------+-------------------------+

mysql> INSERT INTO Received VALUES (\'flotsam\',8,\'2011-01-02\',8);

mysql> SELECT Name,0) |
+---------+-------------------------+
| jetsam  |                       7 | 
| stuff   |                       5 | 
| things  |                       7 | 
| widgets |                       3 | 
+---------+-------------------------+
    

解决方法

采用:
   SELECT i.name,COALESCE(SUM(r.quantity),0) AS total_quantity
     FROM ITEMS i
LEFT JOIN RECEIVED r ON r.name = i.name
                    AND r.invoicedate = \'2011-01-01\'
 GROUP BY i.name
在JOIN之前应用OUTER JOIN的
ON
子句中提供的条件(左,右)。在JOIN之后应用WHERE子句中的条件(针对将表OUTER JOIN连接到的条件)。     

版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。

相关推荐


依赖报错 idea导入项目后依赖报错,解决方案:https://blog.csdn.net/weixin_42420249/article/details/81191861 依赖版本报错:更换其他版本 无法下载依赖可参考:https://blog.csdn.net/weixin_42628809/a
错误1:代码生成器依赖和mybatis依赖冲突 启动项目时报错如下 2021-12-03 13:33:33.927 ERROR 7228 [ main] o.s.b.d.LoggingFailureAnalysisReporter : *************************** APPL
错误1:gradle项目控制台输出为乱码 # 解决方案:https://blog.csdn.net/weixin_43501566/article/details/112482302 # 在gradle-wrapper.properties 添加以下内容 org.gradle.jvmargs=-Df
错误还原:在查询的过程中,传入的workType为0时,该条件不起作用 <select id="xxx"> SELECT di.id, di.name, di.work_type, di.updated... <where> <if test=&qu
报错如下,gcc版本太低 ^ server.c:5346:31: 错误:‘struct redisServer’没有名为‘server_cpulist’的成员 redisSetCpuAffinity(server.server_cpulist); ^ server.c: 在函数‘hasActiveC
解决方案1 1、改项目中.idea/workspace.xml配置文件,增加dynamic.classpath参数 2、搜索PropertiesComponent,添加如下 <property name="dynamic.classpath" value="tru
删除根组件app.vue中的默认代码后报错:Module Error (from ./node_modules/eslint-loader/index.js): 解决方案:关闭ESlint代码检测,在项目根目录创建vue.config.js,在文件中添加 module.exports = { lin
查看spark默认的python版本 [root@master day27]# pyspark /home/software/spark-2.3.4-bin-hadoop2.7/conf/spark-env.sh: line 2: /usr/local/hadoop/bin/hadoop: No s
使用本地python环境可以成功执行 import pandas as pd import matplotlib.pyplot as plt # 设置字体 plt.rcParams['font.sans-serif'] = ['SimHei'] # 能正确显示负号 p
错误1:Request method ‘DELETE‘ not supported 错误还原:controller层有一个接口,访问该接口时报错:Request method ‘DELETE‘ not supported 错误原因:没有接收到前端传入的参数,修改为如下 参考 错误2:cannot r
错误1:启动docker镜像时报错:Error response from daemon: driver failed programming external connectivity on endpoint quirky_allen 解决方法:重启docker -> systemctl r
错误1:private field ‘xxx‘ is never assigned 按Altʾnter快捷键,选择第2项 参考:https://blog.csdn.net/shi_hong_fei_hei/article/details/88814070 错误2:启动时报错,不能找到主启动类 #
报错如下,通过源不能下载,最后警告pip需升级版本 Requirement already satisfied: pip in c:\users\ychen\appdata\local\programs\python\python310\lib\site-packages (22.0.4) Coll
错误1:maven打包报错 错误还原:使用maven打包项目时报错如下 [ERROR] Failed to execute goal org.apache.maven.plugins:maven-resources-plugin:3.2.0:resources (default-resources)
错误1:服务调用时报错 服务消费者模块assess通过openFeign调用服务提供者模块hires 如下为服务提供者模块hires的控制层接口 @RestController @RequestMapping("/hires") public class FeignControl
错误1:运行项目后报如下错误 解决方案 报错2:Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project sb 解决方案:在pom.
参考 错误原因 过滤器或拦截器在生效时,redisTemplate还没有注入 解决方案:在注入容器时就生效 @Component //项目运行时就注入Spring容器 public class RedisBean { @Resource private RedisTemplate<String
使用vite构建项目报错 C:\Users\ychen\work>npm init @vitejs/app @vitejs/create-app is deprecated, use npm init vite instead C:\Users\ychen\AppData\Local\npm-