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Technical Articles

Database

Mysql Tutorial

how to start mysql server on mac terminal

The method of starting MySQL server on the Mac terminal is as follows: 1. Start using mysql.serverstart or sudomysql.serverstart; 2. Check whether the process exists to confirm whether it is running; 3. If the startup fails, troubleshoot insufficient permissions, port occupation, configuration file errors or installation problems. If the command is not found or the startup fails, you can try to run the administrator privileges, check the 3306 port occupancy, check the log file location problems, and ensure that you use a formal method to install it to avoid path or dependency problems.

Jun 27, 2025 am 12:03 AM

Is it necessary to run mysql_secure_installation after I install MySQL

Yes, it is highly recommended to run mysql_secure_installation after installing MySQL for improved security. This tool helps harden the default configuration and prevent unauthorized access by setting a strong root password, removing anonymous users, disabling remote root login, deleting test databases and reloading permissions. When using it, you need to select "yes" to confirm the above operation and enter a strong password. While the same effect can be achieved by manually executing SQL commands, the script is simpler and safer, especially suitable for production environments.

Jun 26, 2025 pm 02:04 PM

MySQL Security

mysql tutorial for data analysis

To use MySQL for data analysis, systematic learning is required. First, design a data structure suitable for analysis: use wide tables and pre-aggregated fields to appropriately redundant data, such as merging orders and user information; modeling time dimensions separately, such as adding date_type fields or date dimension tables; using partition tables to improve efficiency, especially when processing log data, partitioning by date. Secondly, master the key SQL skills: use GROUPBY to cooperate with SUM/COUNT for statistics; use CASEWHEN classification, such as dividing user activity levels; use DATE_FORMAT/WEEK to slice by time; use window functions such as ROW_NUMBER/RANK to rank, such as checking the top three products in each city's sales. Finally optimize query performance: in user_i

Jun 26, 2025 pm 01:57 PM

mysql tutorial about foreign keys and primary keys

Primarykeysuniquelyidentifyrowsinatable,whileforeignkeysestablishrelationshipsbetweentables.Aprimarykeymusthaveunique,non-nullvaluesandeachtablecanhaveonlyone;itcanbeasinglecolumnoracompositeofmultiplecolumns.Foreignkeysreferencetheprimarykeyinanothe

Jun 26, 2025 pm 01:50 PM

change mysql port on mac

To modify the port of MySQL on Mac, first find the configuration file my.cnf, which is usually /etc/my.cnf or /usr/local/etc/my.cnf. You can also find it by the command mysql--help|grep'my.cnf'; secondly, add or modify the port parameters in the [mysqld] part of the configuration file, such as port=3307; then save the file and restart the MySQL service, which can be implemented through brewservicesrestartmysql; finally check whether the port is effective, use the command lsof-i:3307 or mysql-uroot-p-h127.0.0.1-P33

Jun 26, 2025 pm 01:09 PM

mysql workbench error code 1045 access denied for user 'root'@'localhost'

ErrorCode:1045 encountered in MySQLWorkbench, which is usually caused by password error, permission configuration problems or user failure; solutions include: 1. Check whether the user name and password are correct, it is recommended to test login through the command line mysql-uroot-p; 2. If the password is wrong, you can skip permission verification and reset the password. The specific steps are to stop the service, start with skip-grant-tables, update the password and restart the service; 3. Check whether the 'root'@'localhost' exists, if not, you need to create and authorize it; 4. Troubleshoot other reasons such as whether the service is running, whether the configuration file is abnormal, and whether the authentication plug-in is suitable, such as modifying it to mysql_nati

Jun 26, 2025 pm 12:47 PM

mysql tutorial on understanding data types

Choosing the right MySQL data type is critical to performance and storage efficiency. Integer types should be selected reasonably based on the value range and storage space. For example, tinyint is suitable for the status field, int is suitable for most scenarios, and bigint is used for super large values; avoid waste caused by using bigint all, and the unsigned attribute can be used to expand the positive range. String types should be selected as needed, char is suitable for fixed-length fields, varchar is suitable for variable-length content, and text series is used for large text; avoid abuse of varchar(255), and should be optimized according to actual length. Date and time types include date, time, datetime and timestamp, where timestamp accounts for

Jun 26, 2025 pm 12:33 PM

how to upgrade mysql 5.7 to 8.0 on windows

The key points of upgrading MySQL5.7 to 8.0 on Windows include: 1. Back up the database and configuration files, use mysqldump to export all databases and copy the data folder; 2. Download and install the MySQL8.0 MSI package, select the upgrade option or manually replace the ZIP installation file; 3. Update the character set and authentication plug-in settings in the configuration file; 4. Run mysql_upgrade to check and repair the system table; 5. When encountering problems, check the log, force the old authentication method or re-register the service. The entire process needs to be handled with caution to ensure a smooth upgrade.

Jun 26, 2025 am 11:18 AM

mysql tutorial explaining JOINs with examples

JOINscombinedatafrommultipletablesbasedonrelatedcolumns.1.INNERJOINreturnsonlymatchingrows.2.LEFTJOINincludesallrowsfromthelefttable,fillingNULLswhenthere'snomatch.3.RIGHTJOINincludesallrowsfromtherighttable,andFULLJOIN(simulatedviaUNION)combinesallr

Jun 26, 2025 am 11:10 AM

Why am I getting an 'access denied for user 'root'@'localhost'' error after a fresh MySQL install

The problem "accessdeniedforuser'root'@'localhost'" is usually caused by not setting a password, authentication method changes or permission configuration errors. The solution is as follows: 1. If you do not set a password or forget your password, you can try logging in without a password and setting a new password, or resetting through security mode; 2. If you use the new version of MySQL/MariaDB, the default authentication method may be auth_socket, which needs to be modified to mysql_native_password; 3. Ensure that localhost is correctly connected and has access rights, use sudo to run the client or check the GUI tool configuration if necessary; 4. If you cannot log in completely, you can stop the MySQL server.

Jun 26, 2025 am 10:58 AM

How to find duplicate records in a MySQL table?

Finding duplicate records in MySQL requires the use of GROUPBY and HAVING clauses. 1. First, clearly determine the duplicate key fields, such as single fields such as email or name, or combinations of multiple fields; 2. Use SELECT field COUNT() to combine GROUPBY and HAVINGCOUNT()>1 to filter duplicate values, such as SELECTemailFROMusersGROUPBYemailHAVINGCOUNT()>1; 3. If you need to display specific duplicate records, you can implement them through JOIN subquery, such as SELECTu.FROMuserssuJOIN(SELECTemailFROMuser(SELECTemailFROMuser)>1; 3. If you need to display specific duplicate records, you can use JOIN subquery to do so, such as SELECTu.FROMuserssuJOIN(SELECTemailFROMuser

Jun 26, 2025 am 10:45 AM

mysql tutorial for data import from CSV

The key to importing CSV data to MySQL is to make sure the format is correct and use the appropriate commands. First, confirm that the CSV file path is accessible to MySQL, and that the field structure of the target table matches the CSV column; second, it is recommended to use the LOADDATAINFILE command to import, pay attention to setting correct field separators, line breaks, and skipping title lines. In addition, if you are not familiar with SQL operations, you can complete the import through graphic tools such as phpMyAdmin or Navicat; finally, when dealing with common problems, you need to check whether the number of fields is consistent, whether the file encoding is UTF-8, whether the user has FILE permissions, and whether the file path is valid. Follow these steps and the CSV import process will be smoother.

Jun 26, 2025 am 10:32 AM

How to grant privileges to a user in mysql workbench

The key to authorizing users in MySQLWorkbench is to clarify the permission type and operation sequence. 1. Enter the "UsersandPrivileges" interface to manage user permissions; 2. Create a new user or select an existing user for editing; 3. Grant global, database or table-level permissions according to needs and decide whether to enable "Grantoption"; 4. Execute FLUSHPRIVILEGES refresh permissions and test login to ensure that the settings take effect.

Jun 26, 2025 am 10:09 AM

How to export data to CSV in mysql workbench

Exporting data as a CSV file in MySQLWorkbench can be achieved in two ways. 1. Export using query results: After running the SELECT query, click the "Export/Import" icon in the result area, select "ExporttoSelf-ContainedFile", set the file type to .csv and save; 2. Export directly from the table data: Right-click the target table and select "TableDataExportWizard", select the column according to the prompts and set the export path and format to complete the export. Notes include checking the character set to avoid garbled code, checking "Quotioswhenneeded" to handle special characters, and adjusting points as needed

Jun 26, 2025 am 09:45 AM