1.MySQL installation
(1) Double-click the MySQL
that we downloaded from the official website ( 2) Keep clicking Next until you encounter the following interface
(3) Select Typical, it will jump, click Install
(4) Wait for the download to complete, click next
(5) Come to the following interface, click Finish to come to the configuration interface
(6) Click next to start the configuration
(7) Default options, detailed configuration
(8) Continue to select the default development machine
(9) Select default transaction support
(10) Keep defaulting to the next step until you encounter MySQL port 3306 (file download port: 21, Internet port: 80, MySQL port: 3306, Oracle port: 1521)
(11) Select database character set
## (12) Default MySQL service name ; Select the bin directory to configure PATH, and do not configure it manually later; you can also uncheck it and manually configure the environment variables later
(13 ) After setting the password of the super user root, continue to the next step:
# (14) Click Execute until all four check marks are marked. Successful installation!
When we install, MySQL is started by default, but you can also start it manually!
Method 1:
win r Enter services.msc; find MySQL, start and stop manuallyMethod 2:
Open the dos command window as an administrator and enter the following commandnet stop MySQL #停止 net start MySQL #启动
Method 1:
Use the client command line tool provided by MySQL; in the start menu, find the MySQL command line toolMethod 2: Use the dos window to log in
The first direct login method: mysql -uroot -p123456Press Enter directly. If the following interface appears, the login is successful; but this method has disadvantages, others can see us Enter the password
Second login method: first enter: mysql -uroot -p and press Enter, then enter Password, others can’t see our password
4. MySQL perfect uninstallation
Step 1: Re-open our installation package and find the following interface:
Finally click Remove
## Step 2: Delete two files
(1) The MySQL folder under our default installation pathThe above is the detailed content of How to download, install and uninstall MySQL perfectly. For more information, please follow other related articles on the PHP Chinese website!

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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