成人av在线一区二区三区,第九色区av天堂,国产av午夜精品一区二区入口

Article Tags

All
web3.0
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- All
- PHP Tutorial
- Python Tutorial
- Golang
- XML/RSS Tutorial
- C#.Net Tutorial
- C++
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
Database
- All
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- All
- Mac OS
- Linux Operation and Maintenance
- Apache
- Nginx
- CentOS
- Docker
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- All
- VSCode
- sublime
- notepad
- git
- composer
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- All
- Laravel
- YII
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- All
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- All
- IIS
- SEO
- Premiere
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- All
- AI
- It Industry
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- All
- WordPress
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- All
- javaTutorial
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- All
- Windows Series
- LINUX
- MAC
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
Hardware Tutorial
Mobile Tutorial
- All
- Mobile News
- iPhone
- Android Phone
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
Mobile Game Tutorial

Home

Technical Articles

Database

Mysql Tutorial

mysql coalesce function

The COALESCE function is used to return the first non-null value in the parameter list and is suitable for processing NULL data. 1. The basic usage is to replace the NULL value, such as replacing the empty field with the default contact method; 2. It can be used to set the default value in aggregate query to ensure that 0 is returned instead of NULL when there is no data; 3. It can be used in conjunction with other functions such as NULLIF and IFNULL to enhance data cleaning and logical judgment capabilities.

Jul 09, 2025 am 01:09 AM

php java

how to enable binary logging in mysql

To enable MySQL's binary log, you first need to add settings in the configuration file. The specific steps are: 1. Add server-id=1 and log-bin=mysql-bin in the [mysqld] paragraph to enable logs and specify file name prefix; 2. Optionally configure log path and retention policy, such as expire_logs_days=7 to automatically clean logs seven days ago; 3. After modification, restart MySQL service and verify the enabled status through SHOWVARIABLESLIKE'log_bin' and SHOWBINARYLOGS; 4. If you need to clean the logs manually, you can use the PURGEBINARYLOGS command to delete the specific file or before the time.

Jul 09, 2025 am 01:01 AM

Monitoring MySQL Server Performance and Status

To monitor the performance and status of MySQL server, you need to start from four aspects: built-in commands, resource monitoring, tool usage and log checking. 1. Use built-in commands such as SHOWSTATUS and SHOWPROCESSLIST to quickly view the number of connections and running status; 2. Use system commands and MySQL internal mechanisms to monitor the execution efficiency of CPU, memory, disk IO and SQL; 3. Use MySQLWorkbench, Prometheus Grafana, Zabbix or PMM to achieve continuous monitoring and reasonably set the acquisition frequency; 4. Regularly analyze error logs and slow query logs, set thresholds and optimize SQL that is not indexed, so as to promptly discover potential problems and prevent service interruptions.

Jul 09, 2025 am 01:00 AM

mysql performance MySQL status

how to get current quarter from date in mysql

The function to get the quarter where the date is in MySQL is QUARTER(). Use QUARTER(date) to directly return quarterly values ??between 1 and 4; you can also use CURDATE() to obtain the current quarter; if you need to be compatible with other databases or manually calculate, you can extract the month by MONTH(date) and calculate the quarter through formula (month 2) DIV3.

Jul 09, 2025 am 12:50 AM

when should i create an index in mysql

The timing of creating an index includes: 1. Query frequently uses a certain field as a filtering condition, especially when it can significantly reduce the result set, it is suitable to add single columns or composite indexes, but avoid fields with low distinction; 2. Fields that are often used for JOIN operations should be indexed, and the index order should be consistent with the JOIN order; 3. Indexes can be used to avoid additional sorting, pay attention to index direction and order matching; 4. Overwriting indexes are suitable for scenes where all fields are included in the index, reducing back-to-table query, and improving reading efficiency.

Jul 09, 2025 am 12:48 AM

Updating Existing Records in a MySQL Table with Specific Conditions

The key to safely and efficiently updating records in MySQL is to use WHERE conditions and reasonable structures accurately. 1. Use the WHERE clause to limit the update scope to ensure accurate conditions. Use SELECT to check the matching data before update; 2. During batch updates, you can use the CASEWHEN structure to achieve differentiated updates of multiple records to improve efficiency; 3. Pay attention to performance issues, such as adding indexes, avoiding full table scanning, using LIKE and functions with caution, and it is recommended that the test environment be verified first.

Jul 09, 2025 am 12:46 AM

mysql Update records

mysql find and replace in string

In MySQL, the REPLACE() function can replace the string in the field. The syntax is UPDATE table name SET field name =REPLACE (field name, 'old content', 'new content'); 1. This operation is replaced globally and case-sensitive; 2. It is recommended to backup or add WHERE conditional test before execution; 3. The replacement effect can be previewed in SELECT; 4. Pay attention to avoiding error substitution, performance impact and data backup problems.

Jul 09, 2025 am 12:44 AM

how to get last inserted id in mysql

The core method for getting the last inserted ID in MySQL is to use the LAST_INSERT_ID() function, which returns the autoincrement ID generated by the last insertion in the current connection. 1. Get the ID directly after insertion: call LAST_INSERT_ID() immediately after executing the INSERT statement, which is suitable for tables with auto-incremental primary keys; 2. Used in programming languages: For example, PDO extension of PHP calls the function through lastInsertId() and Python's mysql-connector through lastrowid package; 3. Performance when inserting multiple lines: Return the ID of the first insert record, not the last; 4. Notes include: Connection isolation ensures that it is not affected.

Jul 09, 2025 am 12:23 AM

mysql data types explained

ChoosingtherightMySQLdatatypeimprovesstorage,performance,andquerybehavior.1.UseINTforgeneralwholenumbers,TINYINTforsmallranges,DECIMALforexactprecision(e.g.,financialdata),FLOAT/DOUBLEforapproximatescientificvalues,andavoidoverusingBIGINT.2.ChooseCHA

Jul 09, 2025 am 12:04 AM

Working with JSON data type in MySQL

MySQL supports JSON data types introduced since version 5.7 to handle structured and semi-structured data. 1. When inserting JSON data, you must use a legal format. You can use JSON_OBJECT or JSON_ARRAY functions to construct, or pass in the correct JSON string; 2. Updates should use JSON_SET, JSON_REPLACE, JSON_REMOVE to modify some fields instead of the entire replacement; 3. Query can extract fields through JSON_CONTAINS, -> operators, and note that the string value needs to be double quoted; 4. It is recommended to create a generated column and index to improve performance when using JSON type.

Jul 08, 2025 am 02:57 AM

mysql json

Understanding the MySQL optimizer's behavior

The MySQL query optimizer selects the optimal execution plan based on statistical information. The core mechanism is a cost-based model (CBO), which estimates I/O and CPU costs to determine the execution path; 1. Perform ANALYZETABLE regularly to ensure the accuracy of statistical information; 2. Indexes are not always used, such as querying large amounts of data or function operations may fail; 3. It is recommended to use EXPLAIN to view the execution plan, create overlay indexes, and avoid implicit type conversion; 4. The optimizer can be booted through USEINDEX or FORCEINDEX, but be cautious; 5. Rewriting the SQL structure and controlling the connection order can also affect the optimization results. Mastering these logic and combining tool analysis can help to optimize efficiently.

Jul 08, 2025 am 02:56 AM

mysql optimizer

Using JSON Data Type and Functions in MySQL 5.7 and Later

MySQL5.7 natively supports JSON data types, improving the efficiency of processing unstructured data. 1. Use the JSON type to automatically verify the data format and provide special function operation content; 2. When querying, field values ??can be extracted through -> or JSON_EXTRACT(), supporting array element extraction; 3. Use functions such as JSON_SET(), JSON_REPLACE(), JSON_REMOVE() to modify data; 4. You can optimize the query performance of JSON fields by generating virtual columns and establishing indexes; 5. Although it is flexible, JSON type should not be abused, and it needs to be used in combination with actual scenarios.

Jul 08, 2025 am 02:53 AM

Using triggers for database automation in MySQL

A trigger is an automatically executed database object in MySQL that is used to perform predefined SQL operations when a specific event occurs. It can automatically update timestamps, verify or record data changes, maintain redundant fields, implement cascading operations, etc. To create a trigger, you need to specify the trigger timing (BEFORE/AFTER), event type (INSERT/UPDATE/DELETE) and execution logic, such as automatically populating the created_at field with BEFOREINSERT. When using it, you should pay attention to problems such as debugging difficulties, performance impact, high maintenance costs and inapplicability to distributed systems. It is recommended to keep the logic simple and make comments. Common scenarios include recording modification logs, restricting illegal operations, synchronous update of statistics tables and automatic filling

Jul 08, 2025 am 02:53 AM

mysql Database automation

Grouping Data with GROUP BY and Aggregate Functions in MySQL

To extract summary information from the database, use GROUPBY and aggregate functions. GROUPBY can group data by field, and is often used in combination with aggregate functions such as SUM, COUNT, AVG, MAX, MIN, etc.; non-aggregated fields must appear in GROUPBY after SELECT; multi-field grouping is combined in order; HAVING is used to filter grouping results, such as filtering users with a total order amount of more than 1,000.

Jul 08, 2025 am 02:52 AM