聚集索引更新后会不会马上重新排序 今天在QQ群里有人问到下面问题 提问人用的是MYSQL,不过这个问题让我想起了SQLSERVER的万圣节问题 万圣节问题就是因为更新了非聚集索引之后,非聚集索引迅速排序导致的更新错误问题 详见:SQLSERVER中的假脱机 当时我只是
聚集索引更新后会不会马上重新排序
今天在QQ群里有人问到下面问题
提问人用的是MYSQL,,不过这个问题让我想起了SQLSERVER的万圣节问题
万圣节问题就是因为更新了非聚集索引之后,非聚集索引迅速排序导致的更新错误问题
详见:SQLSERVER中的假脱机
当时我只是测试了非聚集索引下面的情况,但是聚集索引下面有没有这种情况呢?
我们修改一下SQLSERVER中的假脱机中的脚本,将建立非聚集索引的那条语句改为建立聚集索引
使用下面SQL脚本建立测试环境
1 USE master Spool Halloween 12 ( 13 ID INT IDENTITY(1, 1), 14 Name VARCHAR(30) , 15 Salary NUMERIC(18, 2), 16 Remark NVARCHAR(3000) 17 ) .( , , ) ,, ,, 3000) ix_Halloween ) Halloween 34 GO

MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

MySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.

SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA

The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.

The steps to build a MySQL database include: 1. Create a database and table, 2. Insert data, and 3. Conduct queries. First, use the CREATEDATABASE and CREATETABLE statements to create the database and table, then use the INSERTINTO statement to insert the data, and finally use the SELECT statement to query the data.

MySQL is suitable for beginners because it is easy to use and powerful. 1.MySQL is a relational database, and uses SQL for CRUD operations. 2. It is simple to install and requires the root user password to be configured. 3. Use INSERT, UPDATE, DELETE, and SELECT to perform data operations. 4. ORDERBY, WHERE and JOIN can be used for complex queries. 5. Debugging requires checking the syntax and use EXPLAIN to analyze the query. 6. Optimization suggestions include using indexes, choosing the right data type and good programming habits.


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