Programmer Think

There are four isolation levels for database transactions: Read Uncommitted: Allow dirty reading, that is, it is possible to read data in other sessions that have not submitted transaction modifications. Read Committed: Only submitted data can be read, which is the default level for most databases such as Oracle. Repeated Read: Repeated Read. ...

objective In some customer response systems, in the face of customer needs, we may need to notify customers by mail or feedback information to customers. For example, the bank billing system needs to process the customer's checking request and send billing email. At this time, the billing data can be written into HTML documents and sent to ...

Hibernate's cache management: Cache is a cache, and it is often the most important means of improving system performance, acting as a reservoir and buffer for data.Cache is particularly important for systems that rely heavily on data read operations.In the case of large concurrency, if each program needs to query the database directly, the perf ...

Previous analysis has said that Windows Manager Service is only responsible for Window management, not for View drawing and layer mixing. This article will analyze how WMS manages windows in the end. When I first came into contact with Android, I felt that Activity seemed to be the encapsulated Window of Google. As long as APP started the new a ...

Introduction to ZooKeeper ZooKeeper(wiki，home，github ) is an open source distributed coordination service for distributed applications.By exposing simple primitives, distributed applications can build higher-level services on top of them, such as synchronization, configuration management, and group membership management.The design is easy to ...

1. Writing Recording Program with c++. 1. PCM audio data is the original audio data, which can not be played by the player. It needs to be added a header to indicate how many channels the sound has, how many sampling rates are, and so on. takePCM audio data is converted to WAV format so that other players can play it. 2. Three parameters shou ...

When analyzing the AWR report of ORACLE, we found that the SQL ordered by Executions (recorded TOP SQL sorted by the number of executions of SQL). This sort shows the number of executions of SQL within the scope of monitoring.) There is a very frequent execution of SQL statements, executing tens of thousands of times in an hour:   update seq$ s ...

MyBatis Develops DAO(Data Access Object) Two ideas: Original Dao Development Method (Writing Dao Interface and Interface Implementation Class DaoImpl, respectively) With MyBatis, proxy development using mapper interface (equivalent to Dao interface) Expected function Implementing CRUD of Single Table with Dao Interface Example program Primi ...

Introduction to haproxy Haproxy provides high availability, load balancing, and proxy based on TCP and HTTP applications, supports virtual hosts, and is a free, fast and reliable solution.HAProxy is particularly useful for web sites that are overloaded and often require session maintenance or seven-tier processing.HAProxy runs on current ...

Before talking about multi-table queries, make a requirement that is not related to multi-table queries. Suppose you have such a column of IDS in Table B +------+ | id | +------+ | 1 | | 2 | | 1 | | 3 | | 4 | | 5 | +------+ Please indicate the serial number for the id column according to the query in table B and displa ...