The following editor will bring you a summary of the special processing statements of mysql's sql statements (must read). The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor to take a look. 1. Update the entire table. If the value of a column in a row of data is empty, then make it equal to the value of another column field UPDATE ot_tgbz set update_day=if(update_day is null, date, update_day); 2. Update the entire table. If a field is greater than 2, update them all to 2; UPDATE ot_user set xingyun_num=if(xingyun_num > 2,2,xingyun_num); 3. Put the shop_goods in the table Replace all URLs containing http://www.jb51.net/ in the thumb field with empty ones. update&nb
1. Example tutorial on processing special sql statements in mysql
Introduction: The following editor will bring you a summary of the special processing statements of mysql's sql statements (must read). The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor and take a look
2. MySQL statement collection: creation, authorization, query, modification
Introduction: 1. User creation, permissions, deletion 1. Connect to MySql Operation connection: mysql -h host address -u username -p user password (Note: u No need to add spaces to root, and the same applies to others) Disconnect: exit (Enter) to open cmd...
3. Oracle query statement collection (oracle basic command collection 1)
Introduction: This article mainly introduces Oracle query statements, which will help novices quickly become familiar with them. The basic syntax of ORACLE helps novices quickly become familiar with the basic syntax of ORACLE. Friends who need it can save it
4. MYSQL Classic Statement Collection - Improvement Chapter
Introduction: Summary: Complete collection of MYSQL classic statements - improvement...
5. MYSQL Classic Statements - Skills
##Introduction: Summary: There are as follows In the table, it is required to frame all the failed grades, and make them just pass on the basis of an increase of 0.1 each time: ...
#6. MYSQL Classic Statement Collection ——Development Chapter
Introduction: Summary: Complete Collection of MYSQL Classic Statements——Development Chapter...
7. MYSQL Classic Statement Collection - Basics
8. Introduction:: This article mainly introduces the classic SQL statements. Students who are interested in PHP tutorials can refer to it.
9.
PHP implements a complete instance of MYSQL statement generation through parameters. Mysql sql statement length limit. Mysql sql statement collection. Mysql sql statement optimization. Introduction: Mysql, sql statement: Complete example of generating MYSQL statement class through parameters implemented by PHP: This article describes the example of generating MYSQL statement class through parameters implemented by PHP. Share it with everyone for your reference, the details are as follows: This class can create SELECT, INSERT, UPDATE and DELETE statements through specified table and field parameters. This class can create WHERE conditions of SQL statements, such as LIKE query statements, using LEFT JOIN and ORDER statements 10. English Sentence Collection PHP+MySQL Manual Injection Statement Recommendation Introduction: English Sentence Collection: English Sentence Collection PHP+MySQL Manual Injection Statement Recommendation: Violent field length Order by num/*matching field and 1=1 union select 1,2 ,3,4,5…….n/*exploit field position and 1=2 union select 1,2,3,4,5…..n/*use built-in function to expose database information version() database() user( ) No need to guess the available fields and database information (some websites are not applicable): and 1=2 union all select version() [Related Q&A recommendations]:
The above is the detailed content of 10 recommended articles about the statement collection. 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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