After following, you can keep track of his dynamic information in a timely manner
Subqueries are queries inside another SQL query, usually appear in SELECT, INSERT, UPDATE or DELETE statements and are surrounded by brackets; it can be nested in multiple locations of the main query, such as WHERE, FROM or SELECT clauses, and are used to provide data conditions or result sets; depending on the returned results, they can be divided into scalar subqueries (one row, one column), row subqueries (one row, multiple columns), table subqueries (multiple row, multiple columns) and existence subqueries (EXISTS); compared with JOIN, subqueries are suitable for filtering or calculating before querying, while JOIN is more suitable for obtaining combined data from multiple tables; when using it, you need to pay attention: subqueries must be wrapped in brackets to avoid excessive nesting affecting readability and performance.
Aug 01, 2025 am 06:47 AM
Formmethod and formtarget are attributes used in HTML to control form submission behavior. 1. Formmethod is used to specify the HTTP method (get or post) at the time of submission, which can overwrite the method attribute of the form. It is suitable for scenarios where different buttons in the same form need to use different submission methods; 2. Formtarget is used to specify the location where the response result is displayed, and can overwrite the target attribute of the form. Common values include _self, _blank, etc., which are suitable for opening results in a new tab without losing the current page data; 3. Both can be applied to the same submit button at the same time, realizing functions such as "previewing in a GET mode in a new tab"; 4. Even if the button bit is
Aug 01, 2025 am 06:46 AM
Use subprocess.Popen with communicate() to interact with external processes safely. 1. Basic usage: start the process through subprocess.Popen(['ls','-l']), communicate() to get stdout and stderr, and the return code is obtained through returncode. 2. Enter data: Set stdin=PIPE, call communicate(input="data") to pass content to the process, such as grep filtering text. 3. Timeout control: communicate(timeout=3) prevents jamming, call kil after timeout
Aug 01, 2025 am 06:46 AM
Notepad uses UTF-8 BOM encoding by default. You can confirm that you are choosing "UTF-8" instead of "UTF-8-BOM" through the "Encoding" menu; 2. If the file contains BOM, you can select "Convert to UTF-8" to remove the BOM and save it; 3. Set the default encoding of the new file to UTF-8 BOM without BOM, and you need to select UTF-8 encoding in "Settings → Preferences → New Document"; 4. Avoid the BOM due to the possibility that the PHP header has been sent errors, JSON parsing failed, script shebang failed, and Git differences are confused; 5. Detect the BOM, you can check whether the first three bytes are EFBBBF through the encoding menu status or use the Hex-Editor plug-in to see if the first three bytes are EFBBBF. Therefore, N
Aug 01, 2025 am 06:45 AM
The answer is to use matplotlib.pyplot to easily draw line charts and basic beautification. 1. Use plt.plot() to draw lines, supporting setting parameters such as color, linestyle, marker, etc.; 2. Add title and axis labels through plt.title(), plt.xlabel(), and plt.ylabel(); 3. Use plt.legend() to display legends, and you need to define labels in plot; 4. Call plt.grid(True) to add grids to improve readability; 5. Finally, use plt.show() to display the image, or use plt.savefig() to save the image. Proficient in these
Aug 01, 2025 am 06:45 AM
A daemonthread is a thread that runs in the background and does not prevent the program from exiting. When the main program ends, the daemonthread will be automatically terminated. 1. It is recommended to use threading.Thread(target=func,daemon=True) method to create daemon threads; 2. You can also use thread.daemon=True before starting, but it cannot be modified after starting. Daemon threads are suitable for background tasks such as logs, heartbeats, polling, etc. There is no need to call join. They will automatically end when the main program exits, but the cleaning work cannot be completed, so they are not suitable for scenarios that require elegant closing.
Aug 01, 2025 am 06:45 AM
MethodsinGoarefunctionswithareceiver,allowingthemtobeassociatedwithaspecifictype,suchasastruct,enablingtype-specificbehavior.2.Unlikefunctions,methodshaveareceiver,usedotnotationforinvocationoninstances,canusevalueorpointerreceiverstocontrolmodificat
Aug 01, 2025 am 06:44 AM
The key to deploying a Go application is to generate static binary files and run them correctly. 1. Use GOOS=linuxGOARCH=amd64gobuild-ldflags="-s-w"-omyapp to build a streamlined static binary file. 2. Transfer binary files to Linux server through scp and grant execution permissions using chmod x. 3. Configure systemd services (such as /etc/systemd/system/myapp.service) to implement process protection and run sudosystemctlenable and start startup services. 4. When deploying cloud platform, Heroku needs to add
Aug 01, 2025 am 06:44 AM
To create a simple HTML page layout, you need to follow the following steps: 1. Use the basic HTML structure, including the div elements of header, navbar, main (including sidebar and content) and footer; 2. Set the global style through CSS, use display:flex to make the sidebar and content sidebar side by side, flex:1 let the content adapt to the remaining space, and use box-sizing:border-box and min-height to ensure the stable layout; 3. Add @media query, and set main to vertical arrangement when the screen width is less than 768px to achieve responsive design. most
Aug 01, 2025 am 06:43 AM
Useimportmoduletoaccessallfunctionsviadotnotation,2.Usefrommoduleimportitemtoimportspecificfunctionsorvariablesdirectly,3.Useimportmoduleasaliasorfrommoduleimportitemasaliastocreateshorthandnames,4.Importyourownmodulesbyplacingtheminthesamedirectoryo
Aug 01, 2025 am 06:43 AM
ThebestwaytodetectraceconditionsinGoistousethebuilt-inracedetectorwiththe-raceflag.1.Rungorun-racemain.goorgotest-race./...toenabletheracedetector,whichidentifiesconcurrentread-writeaccesstosharedvariablesandprovidesdetailedreportsincludinggoroutinet
Aug 01, 2025 am 06:42 AM
OpentheWorddocumentandclickFile>SaveAs.2.ChoosealocationandselectWebPage(.htm;.html)orWebPage,Filteredforcleanercode.3.ClickSave,ensuringtheHTMLfileanditsassociatedassetsfolderarekepttogether.4.Testthewebpageinabrowsertoconfirmproperdisplay,usesim
Aug 01, 2025 am 06:42 AM
Using a custom user model in Django is recommended, especially in the early stage of the project; 2. Inherit the AbstractUser extensible fields and modify the login method, such as setting the mailbox as a unique login field; 3. AUTH_USER_MODEL must be set in advance in settings.py, otherwise subsequent changes will cause foreign keys to break; 4. Create migration and run to generate a database table structure; 5. The admin class can be customized to display new fields in the background; 6. Create superusers to verify whether the configuration is effective; 7. Registration logic can be processed through custom forms; 8. AbstractUser is suitable for extended field scenarios, AbstractBaseUser can be used, and AbstractBaseUser can be used to verify that the configuration is effective; 7. Registration logic can be handled through custom forms; 8. AbstractUser is suitable for extended field scenarios, AbstractBaseUser can be used to customize the field scenarios, and AbstractBaseUser can be used to customize the form.
Aug 01, 2025 am 06:41 AM
Use the @property decorator to create controlled attributes, 1. Use @property to define read-only attributes, and call the getter method when accessing; 2. Use the @property name.setter to add verification logic when assignment; 3. Use the @property name.deleter to define the behavior when deleting attributes; 4. Create dynamically calculated attributes such as area, diameter, etc.; 5. Advantages include encapsulation, data verification, interface compatibility and concise syntax, and ultimately implement intelligent management of attributes without exposing internal data.
Aug 01, 2025 am 06:41 AM
InstallaC compilerlikeMinGW-w64andadditsbindirectorytothesystemPATHtoenablecommand-linecompilation.2.WriteandsaveyourC codeinNotepad witha.cppextension.3.UsetheNppExecplugintocreateascriptthatsavesthefile,changestothecurrentdirectory,compilestheco
Aug 01, 2025 am 06:40 AM
Laravelcontractsareinterfacesthatdefinecoreservices,enablingdecoupledandtestablecodebydependingonabstractionsratherthanimplementations;1.UnderstandthatcontractslikeIlluminate\Contracts\Cache\Repositoryserveasblueprintsforfeatures;2.Usethemintype-hint
Aug 01, 2025 am 06:40 AM
This is a simple login example based on Flask-Login, including user login, session management, and login protection routing. 1. Install flask and flask-login dependencies; 2. Create app.py file and configure Flask-Login, simulate user data and login callbacks; 3. Implement login, logout and protected dashboard routing; 4. Use the template files login.html and dashboard.html for page rendering; 5. Log in with the user name admin and password password123 after running the application. The complete process covers flash messages, form processing and session retention, which is suitable for beginners to quickly master the Flask login mechanism. It is recommended to introduce the database in the future.
Aug 01, 2025 am 06:39 AM
Usethetagfortextthatisnolongeraccurateorrelevant,suchasoutdatedpricesordeprecatedinformation,asitindicatesgenericstrikethroughwithoutimplyingdeletion.2.Usethetagfortextthathasbeenintentionallyremovedfromadocument,asitconveyssemanticmeaningofdeletion,
Aug 01, 2025 am 06:39 AM
OpenWindowsSettingsandgotoApps→Defaultapps→Choosedefaultappsbyfiletype,thensetNotepad forextensionslike.txt,.html,.css,.js,.log,.ini,and.xml.2.IfNotepad isn’tlisted,openControlPanel,gotoPrograms→DefaultPrograms→Setyourdefaultprograms,selectNotepad
Aug 01, 2025 am 06:39 AM
Laravel's database migration management ensures smooth team collaboration and deployment through version control. 1. Migration is a database version control tool that uses PHP code to define schema changes. Each migration includes up() execution changes and down() rollback changes. 2. Use phpartisanmake:migration to create migrations, and quickly generate them with --create or --table parameters; use SchemaBuilder to define structures in up(), such as creating tables, adding fields and foreign keys. 3. Run the migration through phpartisanmigrate, migrate:rollback falls back to the previous batch, migrate:reset resets all
Aug 01, 2025 am 06:38 AM
The SUMPRODUCT function is not limited to product summing, but can also be used for conditional summing, weighted average, etc. 1. The basic usage is to multiply the corresponding elements of multiple arrays and sum, such as calculating the total sales volume and unit price; 2. The conditional summing can be achieved through logical judgment, such as filtering the sales of "East" or "Apple" products, and using the TRUE=1 and FALSE=0 characteristics to combine the array operation; 3. The weighted average value can be calculated, such as multiplying the score and weight and dividing it by the weight sum; 4. When using it, pay attention to the consistency of the scope size, avoiding the entire column reference, treating the text as zero, and using double-negative signs to convert the logical value.
Aug 01, 2025 am 06:38 AM
InGo,identifiersstartingwithacapitalletterareexported(public)andaccessiblefromotherpackages.2.Identifiersstartingwithalowercaseletterareunexported(private)andaccessibleonlywithintheirownpackage.3.Thisruleappliesuniformlytovariables,functions,types,st
Aug 01, 2025 am 06:37 AM
The method to generate SHA-256 hash value using Python's hashlib module is: 1. Import the hashlib module; 2. Create a sha256 object and call the update() method to pass in byte type data (the string needs to be converted with encode('utf-8')); 3. Call hexdigest() to obtain the hex hash value. You can call update() multiple times to implement segmented processing, which is suitable for large files. In the example, the SHA-256 value of "Hello,World!" is dffd6021bb2bd5b0af676290809ec3a53191dd81c7f70a4b28688a
Aug 01, 2025 am 06:36 AM
Use Go's //go:embed directive to embed SQL migration files into binary, 1. Put the SQL file into migrations/directory; 2. Load the files into embed.FS with //go:embedmigrations/*.sql; 3. Use sort.Strings() to sort by file name to ensure migration order; 4. Optionally create a schema_migrations table to record applied migrations; 5. Call applyMigrations in main to execute. This method is suitable for simple applications, avoid external dependencies, and is more convenient to deploy.
Aug 01, 2025 am 06:36 AM
GotoAnythinginSublimeTextisaccessedviaCtrl P(Windows/Linux)orCmd P(macOS),enablingfastnavigation.1.Typeafilenamewithfuzzymatching(e.g.,readme→README.md)toopenfilesquickly,optionallyincludingfolderpathslikesrc/app.2.AfteropeningGotoAnything,type:follo
Aug 01, 2025 am 06:34 AM
Ginispopularforitsperformanceandsimplicity,idealforRESTfulAPIswithbuilt-inmiddlewareandJSONsupport.2.Echooffersaclean,fast,minimalistframeworkwithextensiblemiddlewareandHTTP/2support.3.Fiber,builtonFasthttp,delivershighperformancewithExpress.js-likes
Aug 01, 2025 am 06:33 AM
Static class variables are variables that belong to the class itself and are shared by all instances, and are defined outside the methods in the class. 1. Class variables are accessed and modified by class names, such as Dog.species; 2. All instances share class variables, and the results are the same for printing dog1.species, dog2.species and Dog.species; 3. Modifying class variables through classes will affect all instances; 4. If the instance modifys class variables (such as dog1.species="xxx"), create an instance variable with the same name and no longer share class variables; 5. Common uses include counters, such as Person.count, record the number of instances, and increment each time they are instantiated. Class variables should always be operated using class names to avoid
Aug 01, 2025 am 06:33 AM
Assignauniqueidtothetargetelementonthedestinationpage,suchas.2.CreatealinkusingthehrefattributewiththepageURLfollowedby#andtheid,like.3.Followbestpracticesbyusingdescriptive,space-freeIDsandlinkingtoanyelementwithanid.Thismethodenablesdirectnavigatio
Aug 01, 2025 am 06:32 AM
RuntheWMIDIAGscripttodiagnoseandfixcommonWMIissuesautomatically.2.RebuildtheWMIrepositorybystoppingthewinmgmtservice,renamingtheRepositoryfolder,andrestartingtheservicetotriggerregeneration.3.Re-registerWMIDLLsusingregsvr32andrecompileMOFfileswithmof
Aug 01, 2025 am 06:30 AM
The method of defining and calling functions in Python is: use the def keyword to define the function, followed by parentheses and colons, and the internal code needs to be indented; 1. When defining the function, it can include parameters, such as defgreet(name):; 2. When calling the function, use the function name with brackets, and pass in necessary parameters, such as greet("Alice"); 3. The function can return the value through the return statement, such as defadd(a,b): return b; 4. The function name should use the snake_case nomenclature, and the parameters and return statement are optional. None is returned by default if the return value is not specified.
Aug 01, 2025 am 06:30 AM
