feiyue 03

Tags: carl Cartesian select from color notation establishes connection HTTPDescartes ' accumulation of poor lift When the connection is not established, the name column of the car table and the Brand_Name column of the brand table are queried by the Cartesian product, which is actually multiplied by the two columns for exhaustive, listing all possibilities Table joins: Querying data together for different columns of multiple tables 1. Transverse connection Select column A, column B from table

- Mail protected] ' 10.0.0.% ' identified by ' test123 '; Subnet Mask Configuration method Mysql> grant all in to [e - Mail protected] ' 10.0.0.0/255.255.255.0 ' identified by ' test123 '; mysql> grant all on *.* to [emailprotected]‘192.168.206.%‘ identified by ‘test123‘;Query OK, 0 rows affected (0.00 sec)mysql> select user,host from mysql.user;+---------+---------------+| user | host |+---------+---------------+| root | 127.0.0.1

slowly explain later Sql*plus the default list title results display: The character and date data are left-aligned; The digital data is right-justified. Can use example 1-10 to verify the above conclusions. Example 1-10 Sql> SELECT empno,ename,sal, 2 hiredate,job 3 from EMP; Example 1-10 results Watermark/2/text/ahr0cdovl2jsb2cuy3nkbi5uzxqv/font/5a6l5l2t/fontsize/400/fill/i0jbqkfcma==/dissolve/70/gravity /center "> No words, after writing the article. Save the announcement, the

the form of a two-dimensional table! a two-dimensional table is made up of rows and columns, knowing that the row and column numbers will be able to locate the data in the table! Excel is a two-dimensional table! Easy to use, the basic common SQL language makes it easy to operate relational databases! SQL is supported , so complex queries can be made! easy to maintain, rich integrity (domain integrity, entity integrity, referential integrity, and custom integrity) greatly reduces data redun

1. 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数 select post, group_concat(name) as emp_names, count(id) as emp_num from employee group by post having emp_num ORDER by# 按单列排序, 默认升序 SELECT * FROM employee ORDER BY salary; SELECT * FROM employee ORDER BY salary ASC; # 升序 SELECT * FROM employee ORDER BY salary DESC; # 降序 # 按多列排序 # 先按照age排序，如果年纪相同，则按照薪资排序 SELECT * from employee ORDER BY age, salary DESC; # 练习 1. 查询所有员工信息，先按照age升序排序，如果age相同则按照hire_date降

again after a decentralized operation, which is time consuming. And if your Shard key is reflected in the search criteria, then even if you need to find a few shard scattered, because MONGOs has a direct, will know where to find, the effect will be much better. So to select a Shard key for collection, first determine which items will be used frequently in the search, find the most effective dependencies in these operations, such as a project may not be the kind of good identification can not be

(); }} e.printstacktrace (); } finally { Try { if(Conn! =NULL) Conn.close (); if(Ptmt! =NULL) Ptmt.close (); } Catch(SQLException e) {e.printstacktrace (); } } } Isolation level of a transaction: 4 levels Read uncommited: May cause dirty Reads Read commited: cannot be dirty read, but will appear non-repeatable read Repeat read (REPEATABLE Read): Non-repeatable reads do not occur, but Phantom reads occur Serialization (SERIALIZABLE): Highest isolation level, no phant

Finally, grant all custom script execution permissions uniformly: /data/mysqldata/scripts/*.sh To configure the environment variables for the MySQL user, append a row: echo "export PATH=/data/mysqldata/scripts:\$PATH" >> ~/.bash_profile source ~/.bash_profile At this point, the script can be executed under any path, improving the ease of use of MySQL operations.Four, set the boot automatically start the MySQL serviceOn the basis of the above configuration completion,You can edit the/etc/rc.loca

us.Full case://1. Create a Context object using(vardb =Newentities ()) { //Increase stringsql ="INSERT into UserInfo values (' Zhangsan ', ' 123456 ')"; Db. Database.executesqlcommand (SQL); //Parametric Additionssql ="INSERT into UserInfo values (@UserName, @UserPass)"; varparam =Newsqlparameter[] {NewSqlParameter ("@UserName","Lisi"), NewSqlParameter ("@UserPass","123456") }; Db. Database.

following changes are read before and after the modified output:usingMicrosoft.Framework.ConfigurationModel;usingSystem;namespacegivecase.consoleapps{ Public classProgram { PublicIConfiguration Configuration {Get;Set; } Public voidMain (string[] args) { #region01 read-Write database connection stringConfiguration=NewConfiguration (). Addjsonfile ("Config.json"); stringStrkey ="Data:MSSqlConnection:ConnectionString"; stringConnStr =Configuration.get (strkey); //Read before modificati

that you are calling to change the value of a parameter, you must pass it by reference using the ref or out keyword.Note: Passing parameters by reference also uses a ref-decorated parameter when calling a method.Comparison value passing and reference passingIn summary, a value pass is a copy of the value of a variable that is passed to the method so that the parameter of the method is the same as the value of the argument. Modifying a parameter in a called method is also an update to the data o

Reference URL: http://www.cnblogs.com/mecity/archive/2011/06/11/2078527.html#3060056Mongod Database Startup program MONGO database operator interface startup program1, C:\Program files\mongodb 2.6 standard\bin>mongod--dbpath E:\mongodb\blog\db start database2. Double-click Mongo.exe to start MongoDB operation interfaceIn this way, the interface is not available once the Mongod is closed.Windows Service modeIncrease the Windows service (must be administrator rights to register the service.) Servi

the course table, where two tables have COURSE.CNO=SCORE.CNO connections -- use a table with more data to query the main table, where score is the main table Second, aggregate function 1, Max,min: Take maximum value, minimum value --inquire about the car with the lowest fuel consumption SELECT * FROM car where oil= (select max (oil) from car) 2, Avg: Averaging --Check the average price of the car Where as is used to alias 3, Count: Take the total number --Find out how many cars there are. i

Current Cell Group subscript CreateDate Date Created No way task-Scheduling Task Table Field name Chinese description Data type Length is empty Default value Format Id Id Datestr Date Daystr The first day

Tags: other str server color Dos2unix bash. SH Inquiry Agent1. Architecture 2. Front 2.1 Free QuestionsThe public key confirmation prompt pops up when the server is first connected. Causes an automated task to be interrupted due to the initial connection to the server.The stricthostkeychecking configuration of the SSH client enables the new public key to be automatically received when the server is first connected.　　　　vi /etc/ssh/~]# ssh ip-ouserknownhostsfile=/dev/null - Ostricthostkeychecking

Tags: scale shell basic command mathematical operation data set Shel info programmingThere are some limitations to mathematical operations in the shell. It is mainly divided into the following types:1. square brackets-------support only integer arithmetic[[email protected] documents]$ var1=$[1+5] [email protected] documents]$ echo $var 16[Email protected] documents]$ var2=$[$var 1*2][Email protected] documents]$ echo $var 212[Email protected] documents]$ var1=100[Email protected] documents]$ var

POSTROUTING -s 192.168.100.100 -j SNAT --to 192.168.104.160 B上设置网关为 192.168.100.1ifconfig ens37 192.168.100.1/24ifconfig ens37 192.168.100.100/2410.17 iptables NAT Table Application (middle)A上打开端口转发，再添加iptables规则 echo "1" > /proc/sys/net/ipv4/ip_forward iptables -t nat -A POSTROUTING -s 192.168.100.0/24 -o ens33 -j MASQUERADEB上设置网关 route add default gw 192.168.100.1 ping 192.168.104.160 能ping通，说明与外网可以通信了 添加DNS 119.29.29.2910.18 iptables NAT Table application (bottom)A

Tags: Linux learning7.6 Yum replacing domestic sourcescd /etc/yum.repos.d/rm -r dvd.repowget http://mirrors.163.com/.help/CentOS7-Base-163.repo 或者curl -O http://mirrors.163.com/.help/CentOS7-Base-163.repoyum listcp -r /etc/yum.repos.d.bak/* /etc/yum.repos.d/7.7 Yum Download RPM package安装扩展源epel yum install -y epel-release yum list|grep epelyum下载rpm包 yum install -y 包名 --downloadonly ls /var/cache/yum/x86_64/7/ yum install -y 包名 --downloadonly --downloaddir=路径 yum reinstall -y 包

8.1 Shell Introductionshell 是一个命令解释器，提供用户和机器之间的交互支持特定语法，比如逻辑判断、循环每个用户都可以有自己特定的shellCentOS7默认shell为bash（Bourne Agin Shell）还有zsh、ksh等8.2 Command Historyhistory.bash_history默认1000条变量HISTSIZE/etc/profile 中修改HISTTIMEFORMAT="%Y%m%d %H:%M:%S " 指定历史记录的格式永久保存 chattr +a ~/.bash_history!! //上次执行的命令!n //执行第几条命令!word //word 最近执行命令的前几个字符 [[emailprotected] ~]# echo $HISTSIZE 1000 [[emailprotected] ~]# vim /etc/profile //更改HISTSIZE=2000 [[emailprotected] ~]# echo $HISTSIZE 100

Tags: Linux learning6.1 Compression Packaging IntroductionLinux 常见压缩格式 .zip .gz .bz2 .xz .tar.gz .tar.bz2 .tar.xz6.2 Gzip Compression Toolgzip 1.txtgzip -d 1.txt.gz / unzip 1.txt.gzgzip -# 1.txt // #范围1-9，默认6不能压缩目录,压缩完成后源文件被删除zcat 1.txt.gzgzip -c 1.txt > /tmp/1.txt gunzip -c /root/1.txt.gz > /tmp/1.txt.new-c 源文件保留,必须制定输出的目录 gzip -d -c /tmp/d6z/1.txt.gz > /tmp/d6z/2.txt6.3 bzip2 Compression Toolbzip2 1.txt / bzip2 -z 1.txtbzip2 -d 1.txt.bz2 / bunzip2 1.txt.bz2bzi