Tag Archives: The database
Solve the problem of flash back in Visual Studio 2010
Many people will face such a problem, VS2010 flash back, clearly the program is successful, clearly there is no mistake, the lack of a flash at the end.
The flashback problem is primarily a caching problem, which is added at the end of the program, after the main function
getchar();
getchar();
getchar();
getchar();
Solve the problem.
Reproduced in: https://www.cnblogs.com/yijianzhongqing/p/5208854.html
In the next two years, how do data analysts hang up highly educated engineers? be convinced!
One, data analysis three musketeers
We will analyze the mapping process for Pandas data, including data loading, cleaning, storage, conversion, merging, and remodelling. We will also analyze the mapping process for Pandas data
Second, the MySQL
Multi-platform installation and deployment of MySQL visualization tools and data import and export of multi-table relationship design and field constraints SQL to achieve sales task distribution system
III. Visualized package technology arrangement
Use Django to build a Web project, Web interface to show the principle of communication between browser and Web server routing, view, template, model association principle Seaborn various graphs to create Tableau worksheets, dashboards, story details
Fourth, quantitative analysis data collection
Optimal design algorithm for mathematical modeling of the shape and size of cans Detail the evaluation criteria of the algorithmic model for the study of strategic financial quality factors of “one price”
Five, Hadoop comprehensive analysis
MapReduce and Python programming in detail on the Cascading MapReduce principle analysis Cominer analysis of Spark analysis of SQL distributed and SQL query engine analysis
4. Selected video tutorials + learning documents
These [learning content], only for everyone to study and exchange use, trouble and advertising party please detour!!
Click on the link and leave your contact information, can rapid consultation, free nyc: https://t.csdnimg.cn/StoO
↓↓↓ ↓ with emphasis on ↓↓↓
Today’s society needs, is not only can write code code farmers, but technical and understand the business, can through data analysis, optimize the code to solve the actual business problems of complex talents!
Whether you do research and development, system architecture, or do products, operations, or even management, data analysis is the basic skills, it is no exaggeration to say: data analysis ability, can let you at least the next 10 years of technical career skills.
The author has made an exploratory analysis of the relevant information on the net specifically: 5W monthly salary is only in the middle position. If you want to change careers or work in the data industry, but don’t know where to start, I recommend you study CSDN. It is easier to enter the industry and has broad employment prospects.
Why do I recommend this course to you?
In fact, in any enterprise, each operation link will produce its corresponding data. When there is a problem in the enterprise, correct and complete data analysis can help the decision maker to make a wise and favorable decision. Data analysis plays a vital role in an enterprise.
Therefore, data analysis is like the doctor of the enterprise, which plays a vital role in the survival and development of the enterprise.
Based on this idea, I recommend CSDN’s self-run course “Data Analysis Training Camp” to you, which covers a wide range of content and integrates data collection, cleaning, sorting, visualization and modeling to help you establish the underlying logical thinking of data analysis!
This course is based on the analysis and mining methods often encountered in Python3, teaching you to find problems, form solutions, take actions, feedback and evaluation through data analysis, and form a closed loop, so that your data can give full play to the business value!
How is the course planned?
Scientific and systematic curriculum design
It covers all the technologies that will be applied in the jobs of data analysis engineers in the market, and focuses on the interview questions that must be asked and often asked by algorithms.
Real Stimulating Enterprise Projects
Across real business scenario projects such as finance, advertising, e-commerce, competition and academic experiment, on the basis of the existing courses, the real time training of 11 enterprise-level projects of hot technology has been added.
# Accompany you with a very conscientious teaching service #
Online learning, one-on-one Q&A, real project practice, regular testing, head teacher supervision, live Q&A, homework correction, all of these are designed to ensure that you can follow, finish and learn in the 12 weeks.
In addition, CSDN will also invite some industry celebrities to hold closed-door sharing meetings for students from time to time. Maybe just a little experience sharing in job hunting and daily work can help you avoid many detours.
Lecture given by engineers of front-line big factories
Leaders of front-line big companies such as BAT, Didi and netease serve as teaching tutors, and give in-depth explanations according to the requirements of market data mining positions, so as to directly understand the selection tendency of famous enterprises.
Senior headhunters recommend and guide employment
One to one employment program + resume modification + mock interview + interview tape copy + psychological counseling + free guidance work problems until probation!
Send: 50+ Interview Intensive Topics & AMP; 200+ practical interview question training
In the process of job hunting, CSDN is like your “coach”, providing targeted assistance services in every link of your job hunting.
Again! The most recent Talent Training Program has only 100 places available on a first-come-first-served basis! But also can enjoy super low – price benefits! (It is said that there are only a dozen spots left.)
If you have more questions, such as price, suitable for study, detailed study outline, you can scan the code and reply to the corresponding question.
Emphasis: if you want to test whether you are suitable for the industry, the instructor will send you an audition class + introductory materials + learning map + high-frequency interview questions based on your foundation, these materials are enough to help you test yourself whether you can engage in the relevant position!
Click on the link and leave your contact information, can rapid consultation, free nyc: https://t.csdnimg.cn/StoO
Do you want to get fired? Let’s take a look at the programmer’s resignation tips
Dream eraser, a funny Internet advanced nerd.
The article directories
Write in front 1. Proficient in using rm command 2. Write in reading and writing database operation 3. Do not write comments, do not encapsulate code 4. Forcibly merge code on git 5. No technical resignation tips (thumb up over 200, send to get your boss quit tips O(∩_∩)O
Writing in the front
As the saying goes, write less code, leave less.
Travel the Internet recently, found some tips to leave the job, after reading, the heart was deeply moved
But after careful tasting, found that we programmers are not applicable.
Such as:
- leadership clip dishes you turn the table, we programmers generally not leadership at a table; Leaders open the door you get on the car, our programmers are sitting on duty, generally not on a business trip, business trip generally also leadership drive; Leader K song you cut song, oh ~ KTV singing, I generally hide in the corner; The leader toasts you not to drink,…… ; Leaders listen to your self-drawn,…… ; Leaders drink water you brake,… .
They are clever schemes, but they are not easy for us programmers to learn. Then I learned the following six tips.
“Career Tips”
- > When the Leader says “I’ve been working hard”, you will reply “Don’t be idle and get me a glass of water”, showing your recognition of the Leader’s care. Leader WeChat calls you, you reply “?” “Or” Yes?, simple and efficient. When the Leader asks you why the progress is so slow, you will reply, “Come if you can”, to show your affirmation of his working ability. You are working, and the Leader pretends to be in front of you. Straight back, “Are you teaching me to do something?” “, through humorous language, rhetorical question sentence pattern, play a role in relieving embarrassment. The Leader assigns you a JIRA task and you reply, “That’s it?” , indicates that the requirements are simple and the work can be fully competent. When the Leader asks you to go to the office, you reply, “Don’t you have legs?” “In recognition of his long legs. The Leader sends you a bunch of tasks and says “oh” first. Say more, the job is the same job, just give a response. A coworker asks you, “I notice you’re not doing anything lately?” “, you directly reply “mind your shit”, indicating that the Leader has a clear division of labor and praises the perfect system of the company.
Well, the general skills have been learned, the next formal entry programmer resignation skills reveal secrets.
1. Proficient in using RM command
What is the rm command?Knowledge is not particularly difficult, if you want to learn, can be in the test environment to try rm - rf/ code> or
rm - rf/* code> command.
Note that after running this command, it is best to copy the file a few times after executing it
There's probably nothing the gods can do to keep you from getting fired
If this exit tip doesn't satisfy you, try it in a production environment
Challenge yourself. Give you the authority of the administrator and you will dominate the company
However, after learning this skill, in addition to being able to receive a resignation medal
Maybe you'll get a tip for going to jail
Here buy one get one free for everyone, how much is a gift eraser.
2. Reading and writing database operations are written in the for loop
This exit tip is even more powerful, and it's hard to find out without a Code Review
Read and write database operations, written in the for loop
What subquery, association query, left join, right join, all without
You look up one table, then iterate over the results, and then look up another table
Just be direct
What about multi-table queries?One table, one level loop.
The database link is opened and closed at each level of the loop
select *
lect *
Think of the technical director's helpless face when the server's memory and CPU exploded while reading tens of thousands of data
Is not very cool ~
This is a great exit tip. I hope you enjoy it
What?Sounds like you're complaining, don't you think it's enough?it doesn't matter
In the attached to you a, to delete the delete code>, don't write the
where code> condition, see.
3. Never write comments, never encapsulate code
Don't listen to the technical director, write notes, write documentation, he is to slow down your development efficiency
Then how do we aim at this kind of unreasonable request, and analyze from it to leave a skill
Do the opposite
Never write a comment, let alone a development document, is wasting your valuable time
And the name of the variable, the name of the function, just a, b, c, e, f, g
In addition to simplicity, it comes with encryption
That way you can devote your limited time to development
After all, when you write code, only you and God know what logic is. Maybe in a couple of days, only God knows what logic is.
Second, do not encapsulate the code, from the top to the bottom of the written, program execution, is the most efficient
One function writes a day, one function writes a file
A file to write tens of thousands of lines of code
Then at the end of the code file, write neatly 20 curly braces, that sense of accomplishment must be huge
Don't know what curly braces are?Here's a reference case
}
}
}
}
}
}
4. Git forces merging of code
The tips above can't satisfy you, so you'll love this one, and it's a technical flow
After Git commits the code, what?Have a conflict?
Who dares to modify the same file with me
Forced to merge him
master
anch branch
I'm sure I won't get a resignation letter once or twice
Need to repeat the operation N times, will be able to welcome the resignation notice
What?N times, still can't get the resignation achievement
After merging someone else's branch, make fun of the guy being merged
Make him feel inferior, and then get angry
Let him beat you, then the technical director, must think you are being bullied, and give you a parting award
This is a resignation achievement on its own merits
5. Quietly modify database fields without warning, or change the interface to return data
The trick is to slay the dragon, and when the testing process is found to be faulty, the opportunity arises
Quietly fix one of your own bugs, while silently triggering another
For example, you can modify a field in a table in the database
Then release a patch pack in the name of a system update BUG
The online environment may suddenly crash because it is difficult to see because of the database fields being modified
The more times the system crashes, the better off you'll be
You can also modify the interface data format for the mobile phone, adjust the name of the parameter
In short, fix bugs carefully and write code carefully
Don't let the technical director get the slightest hint that you want to leave
Quietly, he got his resignation letter
666. No skills to quit tips (thumb up over 200, send to your boss quit tips O(∩_∩)O)
What?The above technical level is too high, you technical dishes, can't learn?
No problem, Eraser has carefully prepared you with three easy-to-follow, no-tech quitting tips
There's no barrier to getting started with these skills, so just list the titles
- anonymously teased the company, inadvertently revealed their ID for the meeting screen projection, set automatic QQ reminder, let friends crazy teasing the boss, open the large screen oncoming mode when the technical director demonstrates the project, quietly connected to the projector with Bluetooth, you know the follow-up...
For more tips, please share
the comments section
reading
- 100 cases Python crawler tutorial, fantastic crawler tutorial, subscribe now Python crawler small class, wonderful 9 speak ol>
Today is the 100th day of continuous writing 610
If you have ideas or techniques you'd like to share, feel free to leave them in the comments section.
If you want to build a close relationship with the blogger, follow the blogger, or follow the public account
non-undergraduate programmer
to see how a non-undergraduate programmer grows.
blogger ID:eam eraser
,>e you thumb up, comment, favorites
Android learning notes 03: some problems and solutions in the learning process
In the process of learning Android development encountered a lot of problems, fortunately, the final search through the Internet have been solved. Now some of the problems I encountered in the process of learning Android development and the solutions are sorted out as follows.
1.R.java cannot be updated in real time
Description of the problem: New variables in the res file are not displayed in real time in R.java.
Solution: Select “Project” from the menu bar and check the “Build Automatically” option.
2.LogCat window is not displayed
Problem description: The LogCat window is not displayed in the lower right corner of Eclipse.
Solution: Select “Windows” from the menu bar, then “Show View”, and finally “LogCat”.
“Android Library Projects Cannot Be Launched
“Android Library Projects Cannot Be Launched” error
Solution: Select “Project” in the menu bar, then “Properties”, select “Android” in the pop-up window, and uncheck the IS Library option.
4. “This text field does not specify an InputType or a hint” error after adding EditText control to XML
Problem description: Add EditText control to XML. Control information is as follows.
& lt; The EditText
android: id = “@ + id/EditText”
android: layout_width = “match_parent”
android: layout_height = “wrap_content” & gt; < /EditText>
Error “This text field does not specify an InputType or a hint” at compile time.
Control lacks android:hint and android:inputType information. The android:hint is used to set the default text prompt displayed when EditText is null. Android: InputType is used to set the text type of EditText, which is used to help the input method display the appropriate keyboard type.
Add android:hint and android:inputType information to the control. Add the control information as follows.
& lt; The EditText
android: id = “@ + id/EditText”
android: hint = “0”
android: inputType = “number”
android: layout_width = “match_parent
” Android: layout_height = “wrap_content” & gt; < /EditText>
5. Warning message “Hardcoded string” XXX “, should use @string resource
Problem description: Add Button control in XML, control information is as follows.
& lt; The Button
android: id = “@ + id/mButton_mc”
android: text = “MC”
android: layout_width = “match_parent
” android: layout_height = “wrap_content” & gt;
& lt; /Button>
At compile time, prompt “Hardcoded string” MC “, should use @string resource warning.
The String MC is used in Android :text. You should define the String in string.xml and then use the String resource by calling the String resource name in string.xml. The advantage of doing this is that it can be a complete change and is useful when supporting multiple languages.
Solution: res–> in the project directory; values–> The following is the information for adding the String MC to string.xml.
< resources>
& lt; string name=”mc”> mc< /string>
< /resources>
Then, in the XML that uses the Button control, you use the string by calling its resource name, as follows.
& lt; The Button
android: id = “@ + id/mButton_mc”
android: text = “@ string/MC”
android: layout_width = “match_parent
” android: layout_height = “wrap_content” & gt;
& lt; /Button>
6. Nested weights are bad for performance
Analysis: When using a nested layout, both parent and child layouts use android:layout_weight, but when it is not required, a warning appears as shown in the title.
Solution: Remove the android:layout_weight that is not required for the sublayout, depending on the situation.
7. The solution to an error message “Please ensure that ADB is correctly located at:XXXXX” when starting the emulator
Executed: When using the correct source code, the following error message “Please ensure that ADB is correctly located at ‘D:\AndroidSDK4.0\ Android-SDK-Windows \ Platform-tools \ Adb.exe ‘and can be executed.”
D:\AndroidSDK4.0\ Android-SDK-Windows-Platform-Tools = D:\AndroidSDK4.0\ Android-SDK-Windows-Platform-Tools = PATH
Waiting for HOME (‘ Android.process.acore ‘) to be launched… Waiting for HOME (‘ Android.process.acore ‘) to be launched… The solution to this problem
Phenomena: When the simulator starts, it cannot start after Waiting for a long time (more than 5 minutes). It keeps saying “Waiting for HOME (‘ Android.process.acore ‘) to be launched…”. Information.
Solution: Delete the current emulator and create a new one.
9.Android emulator landscape screen and portrait screen toggle
After the emulator is started, select the emulator and press Ctrl +F11 to switch between landscape and portrait screen of the Android emulator.
10. The imported Android project @Override returns an error
Phenology: When importing the Android project source code downloaded from the Internet into Eclipse, @Override returns an error.
On the project that reported the error, right-click on Properties–>; Java Compiler–> Select 1.6 in Compiler Compliance Level to refresh the project, and the error will not be reported.
Solve the database connection failure of Discuz! Database error (1045) notconnect Forum
A long time ago in their own Tencent cloud server to take a Discuz forum to play, the results today accidentally opened and found the wrong report!
Server error 500 detailed error
Management Tools ->; Internet Information Service (IIS) Manager
Click 500 to fix the detailed error
SQL Union, union all usage and common errors and Solutions
The SQL UNION operator
The UNION operator is used to combine the result sets of two or more SELECT statements.
Note that the SELECT statement within the UNION must have the same number of columns. Columns must also have similar data types. Also, the order of the columns in each SELECT statement must be the same.
The UNION SQL grammar
SELECT column_name(s) FROM table_name1
UNION
SELECT column_name(s) FROM table_name2
Note: By default, the UNION operator picks a different value. If duplicate values are allowed, use UNION ALL.
SQL UNION ALL syntax
SELECT column_name(s) FROM table_name1
UNION ALL
SELECT column_name(s) FROM table_name2
Also, the column name in the UNION result set is always equal to the column name in the first SELECT statement in the UNION.
Error reporting and resolution
When using the UNION operator, the following error can easily be reported:
Parse error: org. Apache. Hadoop. Hive. Ql. Parse. ParseException: line 5-0 always recognize input near “and” (” and “the UNION, ‘ ‘SELECT’ set in the operator
Simplify the code used as follows:
SELECT
device_id
FROM
tableA
UNION
(SELECT
device_id
FROM
tableB as a1
INNER JOIN tableC as a2
on a1.device_id = a2.device_id
)
This is mainly because the UNION operator can only join fields to fields, but not fields to tables or tables, even if the number of fields and their names and formats are the same.
Therefore, you can’t have parentheses around the UNION operator, because it’s easy for SQL to determine that this is a subquery/table and therefore to report an error when joining
The solution
- > SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>> SELECT FROM TABLE D OL>
Matters needing attention
- > Multiple UNION operators can be used in SQL statements. SELECT statements that use the UNION operator cannot contain their own ORDER BY or COMPUTE clauses. You can only use an ORDER BY or COMPUTE clause on the final combined result set (that is, after the last SELECT statement). The GROUP BY and HAVING clauses can be used in SELECT statements that use the UNION operator. By default, SQL Server 2005 evaluates statements containing the UNION operator from left to right. You can specify the order of evaluation using parentheses (I haven’t tested this thoroughly on any other platform, so avoid parentheses altogether, so if you need to specify the order of evaluation, you can simply write that part of the evaluation at the beginning of your SQL statement).
Win10 installation PostgreSQL error running… And installation process
On error figure,
solving to install another version click here to download
this blog to find solutions from here https://blog.csdn.net/weixin_44150643/article/details/106739793
installation steps
Custom installation path
Next
Next
Set your own password.
next
next
click install good, (ps: installation package to administrator program is running, or sometimes errors as follows:).
a non-fatal error occured whilst loading database modules.
This is the PostgreSQL installation process and errors.
Solution of duplicate entry ‘value’ for key ‘field name’ in MySQL
II. Question interpretation:
Duplicate entry… for key… This error is caused by the repetition of the unique value of the primary key. This error will be reported when the unique value of the primary key is repeated during database modification or insert operation. Sometimes, this error will be reported for table operations when there are multiple identical primary keys.
(p) If you want to import data from one table into another table, you will get an error in using the primary key field.
Three, solutions:
First, if the primary key is not a required field, the primary key is not used
The second way is to remove the duplicate from the table and start the operation
Thanks for watching!
The MySQL service suddenly hangs up with the error message can’t connect to MySQL server on ‘localhost’ (10061)
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘localhost’ (10061)
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘localhost’ (10061)
>
> Services.msc (open service) –>; Find MySQL in the services list –>; Right-click MySQL and click Start
However, sometimes you have installed MySQL, but there is no MySQL in the service list. What can you do?
(1) Open CMD (run C:\Windows\System32\cmd.exe as an administrator),
(2) Use CD to change the directory to bin directory of MySQL Server 5.6;
C:\Program Files\MySQL\MySQL Server 5.6\bin> mysqld.exe -install
(4) When there is Service successfully installed, it means that MySQL Service successfully installed.
At this point, the MySQL service is already present in the computer service.
Matters needing attention
The CMD command opens and runs under the bin directory where MySQL is installed:
> > > Mysqld –install (“mysqld”, not “mysql”)
Install/Remove of the Service Denied
Install/Remove of the Service Denied
open CMD and run it as an administrator.
When: Service successfully installed. Indicates that the service is installed successfully.
Idea: server returns invalid timezone. Need to set ‘servertimezone’ property
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