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Posted on Edited on In Symbols count in article: 1.3k Reading time ≈ 1 mins.

在oracle中直接有decode函数 decode(cola,null,0)

表示如果cola为空，赋值为0

在mysql中的具体实现如下，

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mysql> describe book;
+---------+--------------+------+-----+---------+----------------+
| Field   | Type         | Null | Key | Default | Extra          |
+---------+--------------+------+-----+---------+----------------+
| book_id | bigint(20)   | NO   | PRI | NULL    | auto_increment |
| name    | varchar(100) | NO   |     | NULL    |                |
| number  | int(11)      | NO   |     | NULL    |                |
+---------+--------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

mysql> select * from book;
+---------+-------------------------+--------+
| book_id | name                    | number |
+---------+-------------------------+--------+
|     123 | 123                     |    122 |
|    1000 | Java程序设计             |      5 |
|    1001 | 数据结构                 |      9 |
|    1002 | 设计模式                 |     10 |
|    1003 | 编译原理                 |     10 |
|    1004 | MySQL从删库到跑路         |    100 |
|    1005 | 活着                     |     10 |
|    1232 | 11111                    |    124 |
|    2001 | 测试                     |   2001 |
|   10064 | 老鼠爱大米               |  10088 |
|   10066 | 老鼠爱大米               |   1008 |
|   10088 | 测试宝典                |   1008 |
|   10096 | maven实战               |  10096 |
|   11111 | 111111                  |  11111 |
|   12311 | 都懂得                  |   1222 |
|  123222 | 222                     |   1111 |
+---------+-------------------------+--------+
16 rows in set (0.00 sec)

mysql> select if(count(b.book_id)=16,"十六","不是十六") '结果' from book b;
+--------+
| 结果   |
+--------+
| 十六   |
+--------+
1 row in set (0.00 sec)

mysql> select case count(b.book_id) when 16 then '十六' else '其他' end as '结果' from book b;
+--------+
| 结果   |
+--------+
| 十六   |
+--------+
1 row in set (0.00 sec)

Posted on Edited on In Symbols count in article: 4.8k Reading time ≈ 4 mins.

到处搜了一下也没有看到专门做好的jar包

真实的目录结构如下：

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C:\1\hisenyuan\build.png
C:\1\hisenyuan\DSCN6812.JPG
C:\1\hisenyuan\test\test\hello.zip
C:\1\hisenyuan\test\hisenyuan.zip
C:\1\hisenyuan\test\test.txt
C:\1\hisenyuan\test\test\hello\hello.txt
C:\1\hisenyuan\tomcat.png

压缩包的目录结构如下：

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build.png
DSCN6812.JPG
test\hello.zip
test\hisenyuan.zip
test\test.txt
test\hello\hello.txt
tomcat.png

全部代码如下：

Read more »

Posted on Edited on In Symbols count in article: 830 Reading time ≈ 1 mins.

IDEA上搭建dubbo服务的简单过程

只是简单的让例子在IntelliJ IDEA跑起来

目前是最新的版本：2.5.4-SNAPSHOT

本文档更新时间：2017年04月19日01:08:02

一 、安装zookeeper

参考链接：ubuntu apt-get安装zookeeper

二、Idea clone本项目

导出项目之后，配置一下tomcat，添加dubbo-admin：war到tomcat中

项目github地址：https://github.com/hisen-yuan/dubbo

三、启动tomcat，即可访问dubbo管理后台

默认账号：root

默认密码：root

四、启动服务提供者&消费者demo

  1. 修改dubbo-demo-consumer配置文件中的注册中心地址
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/dubbo/dubbo-demo/dubbo-demo-consumer/src/test/resources/dubbo.properties
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#dubbo.registry.address=multicast://224.5.6.7:1234
#使用本地的zookeeper做注册中心
dubbo.registry.address=zookeeper://127.0.0.1:2181
  1. 修改ubbo-demo-provider配置文件中的注册中心地址
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/dubbo/dubbo-demo/dubbo-demo-provider/src/test/resources/dubbo.properties
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#dubbo.registry.address=multicast://224.5.6.7:1234
#使用本地的zookeeper做注册中心
dubbo.registry.address=zookeeper://127.0.0.1:2181
  1. 分别启动dubbo-demo下ubbo-demo-provider、dubbo-demo-consumer下的测试方法

即可在后台看到有服务在运行

Posted on Edited on In Symbols count in article: 1.5k Reading time ≈ 1 mins.

表结构，数据内容如下。

需求是：查找出每个年级，年纪最大的人的名字。

个人的思维只停留在

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mysql> select name, max(age),grade from  stu group by grade;
ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'hisen.stu.name' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

mysql> SELECT A.* FROM stu A INNER JOIN (SELECT MAX(AGE) AS MAX_AGE,GRADE FROM stu GROUP BY GRADE ) B ON A.GRADE = B.GRADE AND A.AGE= B.MAX_AGE;
+----+------+------+-------+
| id | name | age  | grade |
+----+------+------+-------+
|  3 | c    |   13 |     1 |
|  6 | f    |   13 |     2 |
+----+------+------+-------+
2 rows in set (0.00 sec)

折腾了一会自己不知道怎么解决，后来倒是解决了。

具体过程如下：

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mysql> describe stu;
+-------+---------+------+-----+---------+----------------+
| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+
| id    | int(11) | NO   | PRI | NULL    | auto_increment |
| name  | char(1) | YES  |     | NULL    |                |
| age   | int(11) | YES  |     | NULL    |                |
| grade | int(11) | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> select * from stu;
+----+------+------+-------+
| id | name | age  | grade |
+----+------+------+-------+
|  1 | a    |   11 |     1 |
|  2 | b    |   12 |     1 |
|  3 | c    |   13 |     1 |
|  4 | d    |   11 |     2 |
|  5 | e    |   12 |     2 |
|  6 | f    |   13 |     2 |
+----+------+------+-------+
6 rows in set (0.00 sec)

mysql> select max(name), max(age),grade from  stu group by grade;
+-----------+----------+-------+
| max(name) | max(age) | grade |
+-----------+----------+-------+
| c         |       13 |     1 |
| f         |       13 |     2 |
+-----------+----------+-------+
2 rows in set (0.01 sec)

Posted on Edited on In Symbols count in article: 2.6k Reading time ≈ 2 mins.

一、配置ubuntu国内镜像，这里推荐阿里云，右上角搜索：换阿里云源

二、安装docker

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sudo apt-get update
sudo apt-get install \
     linux-image-extra-$(uname -r) \
     linux-image-extra-virtual

安装docker包

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sudo apt-get install \
     apt-transport-https \
     ca-certificates \
     curl \
     software-properties-common

添加docker官方GPG秘钥,留意最后那个符号也要复制

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curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

安装稳定版仓库

Read more »

Posted on Edited on In Symbols count in article: 675 Reading time ≈ 1 mins.

配置文件：

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yourPath\maven-3.3.9\conf\settings.xml

找到里面的，添加镜像即可

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<mirrors>
</mirrors>

这里写的是被镜像的ID

如果写成：* (星号)

所有的请求都会到这个镜像上，包括各种本地库

注意：千万不要配成***

否则内网的仓库或者你配的镜像里面没有一下jar包的时候不会去别的地方搜索

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<!--阿里云：速度挺快-->
<mirror>
	<id>nexus-aliyun</id>
	<mirrorOf>central</mirrorOf>
	<name>Nexus aliyun</name>
	<url>http://maven.aliyun.com/nexus/content/groups/public</url>
</mirror>

<!--谷歌：北京速度不错-->
<mirror>
  <id>google-maven-central</id>
  <name>Google Maven Central</name>
  <url>https://maven-central.storage.googleapis.com</url>
  <mirrorOf>central</mirrorOf>
</mirror>

Posted on Edited on In Symbols count in article: 260 Reading time ≈ 1 mins.

第一种：

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select *
  from (select t.*, rownum rn
          from (select * from EW_AUTH_FLOW) t
         where rownum <= 5)
 where rn > 2;

第二种：

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select *
  from (select t.*, rownum rn from ew_auth_flow t where rownum <= 5)
 where rn > 2;

第三种：

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select *
  from (select t.*, rownum rn from ew_auth_flow t)
 where rn between 2 and 5;

Posted on Edited on In Symbols count in article: 304 Reading time ≈ 1 mins.

在使用jedis的时候出现这个问题：

redis.clients.jedis.exceptions.JedisConnectionException:Java.net.SocketException:Software caused connection abort: recv failed

我是windows上Java运行，然后redis是在虚拟机的，通过映射访问

解决办法：

编辑redis配置文件：

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sudo vi /etc/redis/redis.conf

找到

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bind 127.0.0.1

改成

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bind 0.0.0.0

改完之后重启redis

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service redis restart

即可。这跟mysql一样，允许任何ip连接！