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In Spring framework, we often use @Transactional annotation to do transactions, but transactions do not guarantee validity; The following are the problems I have encountered, which are not necessarily correct, and can be used as a reference. Ma ...

Summary of sql statements Exercise 1: //Create a Category Table: create table category( cid int primary key auto_increment, cname varchar(10), cdesc varchar(31) ); insert into category values(null,'Mobile Digital','Electronic product'), (null,'Shoe ...

Recently, I studied the underlying code of Mybatis, and prepared to write a small tool to operate the database, which realized some functions of Mybatis. 1. SQL statements are configured in mapper.xml. 2. Support input of int, String and custom data ...

Examples of Oracle Trigger Usage Brief introduction of flip-flop The definition of a trigger means that when a condition holds, the statement defined in the trigger will be automatically executed. Therefore, triggers do not need to be called arti ...

First look at a chestnut EXPLAIN select * from employees where name > 'a'; If using name index to find data needs to traverse the name field joint index tree, and then according to the traversed primary key value to the primary key index tree to find the final data, the cost is higher than the full table scan. Overlay index optimization c ...

Preface How should we investigate and analyze Mysql deadlock? There was an insert on duplicate deadlock problem on the line before. Based on this deadlock problem, this paper will share the process of investigation and analysis, hoping to be helpful to everyone. Deadlock case recovery Table structure: CREATE TABLE `song_rank` ( `id` int(11) N ...

Links to the original text: https://www.cnblogs.com/zhuanzhuanfe/p/10324700.html Basic concepts GraphQL GraphQL is a query language for the API, developed by Facebook and open source, and runs on the server side using a type-based syst ...

Scrapy scrapy framework, asynchronous crawler framework. Synchronization and Asynchronization Synchronization: The next method relies on the previous method. If the previous method is not finished, the next method will not be executed. Asynchronou ...

A master once said that he knows the database he manages as well as his wife. Personally, he thinks it contains two aspects of understanding: 1. At the level of stability, more attention is paid to high-level measures such as high availability, separation of reading and writing, load balancing, disaster preparedness management and so on. 2. A ...

oracle 11g supports automatic partitioning, but partitioning must be set when creating tables. If an existing table needs to be partitioned, it is necessary to rename the current table, create a new table, copy the data to the new table, and the ...