centralized database advantages and disadvantages

Label: Why do you want to create an index? This is because creating an index can greatly improve the performance of the system.First, by creating a unique index. To ensure that each row of unique data is in a database table.Second, high-speed data retrieval can be greatly accelerated, which is the most basic reason to create an index.Third. This is particularly relevant in terms of achieving the data's textual integrity.The same can significantly redu

that the composite column length cannot be too long; In a composite index, all columns must be from the same table, and composite columns cannot be created across tables In a composite index, the order of the columns is very important, so the order of the columns is carefully arranged, in principle, the most unique column should be defined first, for example, the index on (col1,col2) is not the same as the index on (col2,col1), because the order of the two-indexed columns is different ; for the

composite index, the total length of the columns that make up the composite index cannot exceed 900 bytes, which means that the composite column length cannot be too long; In a composite index, all columns must be from the same table, and composite columns cannot be created across tables In a composite index, the order of the columns is very important, so the order of the columns is carefully arranged, in principle, the most unique column should be defined first, for example, the index on (col1

DatabaseType Characteristics Advantages Disadvantages relational databaseSQLite, Oracle, MySQL 1, relational database, refers to the use of a relational model to organizeDatabase of data;2, the most characteristic of relational database is the consistency of affairs;3, in simple terms, the r

information of the database in one XML, and LINQ to SQL has two ways, one is put into XML, we are called EXTERNL Mapping, and one is in the form of attribute, in each property. Of course, I did not use the NHibernate, only from the data to get these messages, so can not give more comparison. 2. The disadvantages of LINQ to SQL A long time ago, a netizen asked such a question. He had a DataView in the int

Label:The benefits of a relational database:1. Maintain data consistency (transaction processing)2. Due to standardization, the cost of updating data is small (the same fields are basically only one place)3. Complex queries such as joins can be madeOne of the best advantages of relational databases is the ability to maintain data consistency.The lack of a relational database:Not good at handling1. Write pro

incorrect. please correct me and grow together. 　　CodeIgniter Advantages: 1. the configuration is simple. all configurations are configured using PHP scripts with high execution efficiency. it has the basic routing function and can perform a certain degree of routing. it has the preliminary Layout function, ability to make a certain degree of interface appearance; database layer encapsulation is good, wit

may be immature or incorrect. please correct me and grow together. 　　CodeIgniter Advantages: 1. the configuration is simple. all configurations are configured using PHP scripts with high execution efficiency. it has the basic routing function and can perform a certain degree of routing. it has the preliminary Layout function, ability to make a certain degree of interface appearance; database layer encapsu

Comparison of the advantages and disadvantages of several mainstream PHP frameworks, and comparison of the advantages and disadvantages of the php framework PHP is a popular open-source server-side scripting language at home and abroad. It can meet the development needs of large, medium and small projects. We will intr

Mysql index types and advantages and disadvantages, mysql index advantages and disadvantages An index is a special file (an index on an InnoDB data table is an integral part of a tablespace) that contains reference pointers to all records in the data table.Note:[1] indexing is not omnipotent! Indexing speeds up data re

Original Source: in the Milky Way I don't want to spend a lot of time describing what gevent is. I think it's enough to make a summary on its official website: "Gevent is a coroutine-based Python network library. It uses the high-level synchronization API provided by greenlet to encapsulate libevent event loops ." Next, I will describe how to use gevent in an internal project in mixpanel. For this article, I also wrote a few small performance tests. (Whipped up, which is confusing here --)

functions in Hibernate and toplink. It can be used together with Java SE and Java EE applications. you need to use an EJB container or not. What are the disadvantages of JPA? Because it is very new, the JPA specification may have to go through important developments to become very stable. JPA is a specification rather than a product. You need the provider to provide an implementation to obtain the advantages