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MySQL的LAST_INSERT_ID用法 LAST_INSERT_ID() 自动返回最后一个INSERT或 UPDATE 查询中 AUTO_INCREMENT列设置的第一个表发生的值。MySQL 的LAST_INSERT_ID 的注意事项:第一 、查询和插入所使用的Connection对象必须是同一个才可以,否则返回值是不可预料的。mysql> SELECT LAST_INSERT_ID(); -> 100使用这函数向一个给定Connection对象返回的值是该Connection对象产生对影响AUTO_INCREMENT列的最新语句第一个AUTO_INCREMENT值的。这个值不能被其它Connection对象的影响,即它们产生它们自己的AUTO_INCREMENT值。 第二 、LAST_INSERT_ID 是与table无关的,如果向表a插入数据后,再向表b插入数据,LAST_INSERT_ID返回表b中的Id值。第三 、 假如你使用一条INSERT语句插入多个行, LAST_INSERT_ID() 只返回插入的第一行数据时产生的值。其原因是这使依靠其它服务器复制同样的 INSERT语句变得简单。mysql> INSERT INTO t VALUES -> (NULL, ‘Mary’), (NULL, ‘Jane’), (NULL, ‘Lisa’);mysql> SELECT * FROM t;| id | name |+—-+——+| 1 | Bob || 2 | Mary || 3 | Jane || 4 | Lisa |mysql> SELECT LAST_INSERT_ID(); //这就是我要说明的关键问题。| LAST_INSERT_ID() || 2 |虽然将3 个新行插入 t, 对这些行的第一行产生的 ID 为 2, 这也是 LAST_INSERT_ID()返回的值。第四 、假如你使用 INSERT IGNORE而记录被忽略,则AUTO_INCREMENT 计数器不会增量,而 LAST_INSERT_ID() 返回0, 这反映出没有插入任何记录。
一般情况下获取刚插入的数据的id,使用select max(id) from table 是可以的。但在多线程情况下,就不行了。在多用户交替插入数据的情况下max(id)显然不能用。这就该使用LAST_INSERT_ID了,因为LAST_INSERT_ID是基于Connection的,只要每个线程都使用独立的Connection对象,LAST_INSERT_ID函数将返回该Connection对AUTO_INCREMENT列最新的insert or update操作生成的第一个record的ID。LAST_INSERT_ID是基于单个connection的, 不可能被其它的客户端连接改变。
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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.

MySQL is suitable for beginners because: 1) easy to install and configure, 2) rich learning resources, 3) intuitive SQL syntax, 4) powerful tool support. Nevertheless, beginners need to overcome challenges such as database design, query optimization, security management, and data backup.

Yes,SQLisaprogramminglanguagespecializedfordatamanagement.1)It'sdeclarative,focusingonwhattoachieveratherthanhow.2)SQLisessentialforquerying,inserting,updating,anddeletingdatainrelationaldatabases.3)Whileuser-friendly,itrequiresoptimizationtoavoidper

ACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.

MySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.

MySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.


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