Composite Primary Key In Database

Designing 1 applications doesn't seem to be difficult, but it's not easy to achieve the optimal performance of the system. There are many choices in development tools, database design, application structure, query design, interface selection, and so on, depending on the specific application requirements and the skills of the development team. This article takes SQL Server as an example, discusses the application performance optimization techniques from the perspective of the background database, and gives some useful suggestions. 1 database design to achieve optimal performance in a good SQL Server scenario, the key is to have 1 ...

"Guide" the author (Xu Peng) to see Spark source of time is not long, note the original intention is just to not forget later. In the process of reading the source code is a very simple mode of thinking, is to strive to find a major thread through the overall situation. In my opinion, the clue in Spark is that if the data is processed in a distributed computing environment, it is efficient and reliable. After a certain understanding of the internal implementation of spark, of course, I hope to apply it to practical engineering practice, this time will face many new challenges, such as the selection of which as a data warehouse, HB ...

MySQL database sql statement commonly used optimization methods 1. Query optimization, should try to avoid full table scan, should first consider where and order by the columns involved in the establishment of the index. 2. Should be avoided in the where clause on the field null value judgment, otherwise it will cause the engine to abandon the use of indexes and full table scan, such as: select id from t where num is null You can set the default value of num 0, to ensure that Num column table does not null value ...

MySQL optimization is very important. The most common and most needed optimization is limit. 　　The limit of MySQL brings great convenience to paging, but when the amount of data is large, the performance of limit is reduced dramatically. The same is 10 data select * FROM Yanxue8_visit limit 10000,10 and select * from Yanxue8_visit limit 0,10 is not a quantitative level ...

Is confused, hesitation, complain of E-commerce professional students, you good: This letter is written to the freshmen, but I believe that any level or even graduated from the E-commerce professional students have a role. Every year I can see and hear too many e-commerce majors complaining, yesterday, my alma mater, Xiangtan University, a classmate of electronic commerce and told me that now 07 class freshman was hit very seriously, at the same time, 05, 06 students are also complaining, complain all over the sky, and even a few students have turned professional. In spite of all these years, I have seen no ...

2010 should be remembered because SQL will die this year. This year, the relational database is on the verge of falling, and this year developers found they no longer needed long, laborious columns or tables to store data. 2010 will be the starting year for document databases. Although this momentum has lasted for many years, it is now the era of more and broader document-based databases. From cloud-based Amazon to Google, a large number of open source tools, and the ensuing CouchDB and MongoDB. So what is MongoD ...

Choosing new hardware, storage, and other datacenter infrastructures for large data is a new challenge for IT professionals. Large data is unstructured information with unprecedented scale and form. It includes video, images, and semi-structured data (such as e-mail and text that is common on the web). 　　With more and more sensor-based mobile web monitoring devices and output data, the amount of data available continues to grow exponentially. The pressure to implement big data strategies often comes from the top, because managers believe that companies that can effectively use data will have greater advantages than those who are lagging behind ...

When an enterprise migrates its core IT systems to a private cloud or public cloud network, the work is not over. 　　Now there is a different set of technical issues that need to be addressed: how to manage the cloud to ensure that the enterprise's investment returns, providing the desired efficiency and return on investment. Cloud management and cloud monitoring have become more important as the Amazon EC2 (Flex Computing Cloud) Service outage occurred this April. In that incident, the IT field saw what would happen when the cloud environment encountered a failure ...

The hardware environment usually uses a blade server based on Intel or AMD CPUs to build a cluster system. To reduce costs, outdated hardware that has been discontinued is used. Node has local memory and hard disk, connected through high-speed switches (usually Gigabit switches), if the cluster nodes are many, you can also use the hierarchical exchange. The nodes in the cluster are peer-to-peer (all resources can be reduced to the same configuration), but this is not necessary. Operating system Linux or windows system configuration HPCC cluster with two configurations: ...

Some tests are being done lately, with partial support for a smooth beta of the product. The following is the test of the Desktop. The first part: Windows programming UI design 1. Background introduction UI is the user interface (user-interface), is the interface between people and tools. In the process of human-machine interaction, it must be through the interface. This interface is actually reflected in every aspect of our lives, for example, when we drive the steering wheel and dashboard is this interface, watching TV when the remote control and the screen is this interface, the keyboard when using the computer ...