What are the relational databases
Currently the mainstream relational databases are Oracle, DB2, MicrosoftSQLServer, Microsoft Access, MySQL and so on.
The relational model means a two-dimensional table model, and thus a relational database is a data organization consisting of two-dimensional tables and the links between them.
Oracle is the world’s first open commercialized relational database management system introduced in 1983. It uses the standard SQL structured query language, supports a variety of data types, provides object-oriented storage of data support, with the fourth generation of language development tools, support for Unix, WindowsNT, OS/2, Novell and other platforms. In addition, it also has a good parallel processing capabilities.Oracle products are mainly composed of Oracle server products, Oracle development tools, Oracle applications, but also microcomputer-based database products. Mainly to meet the demand for banking, finance, insurance and other enterprises, business development of large-scale database.
SQL is Structured Query Language (SQL), SQLServer first appeared in 1988, at that time can only be run on OS/2 operating system.
December 2000 Microsoft released the SQLServer2000, which can run on Windows NT/2000/XP and other operating systems, is a database management system that supports a client/server architecture, which can help organizations of all sizes manage data.
With a growing user base, SQLServer is becoming more and more perfect in terms of ease of use, reliability, shrinkability, data warehouse support, and system integration. In particular, SQLServer’s database search engine can run on top of most operating systems and is optimized for querying massive amounts of data. SQLServer has now become one of the most widely used database products.
Because the use of SQLServer not only to master the operation of SQLServer, but also to be able to master the operation mechanism of WindowsNT/2000Server, as well as the SQL language, so the non-specialists have some difficulty in learning and using.
Large-scale relational database management system Sybase launched in 1987, can run on OS/2, Unix, WindowsNT and other platforms, which supports the standard relational database language SQL, using the client/server model, using an open architecture to realize the network environment, the nodes on the database interoperability. It supports the standard relational database language SQL, uses the client/server model, and adopts the open architecture, which can realize the database interoperability of the nodes in the network environment. Advanced technology, excellent performance, is the development of large and medium-sized database tools.Sybase products are mainly composed of server products SybaseSQLServer, client products SybaseSQLToolset and interface software SybaseClient/ServerInterface, as well as the famous database application development tools PowerBuilder.
Common relational databases are?
MySQL, SQLServer, Sybase, DB2, Oracle, Access, etc.
What are the relational databases?
What are the relational databases?
What do you need so many for? Most databases nowadays are relational databases ah. Oracle, SQLServer, Sybase, Informix, access, DB2, mysql, vfp, NPC gold warehouse (domestic, I’ve used) as long as you think you can, what xml can be used as a relational database ah. Exactly 10. I hope my answer is helpful to you!
What are the commonly used relational databases
Relational model refers to the two-dimensional table model, and thus a relational database is a two-dimensional table and its linkage between the composition of a data organization. The current mainstream relational database Oracle, DB2, MicrosoftSQLServe radical, Microsoft Access, MySQL and so on.
What are the relational databases
Large ones are:
Oracle, SQL Server, DB2, Mix, Sybase, etc.
Open-source ones are:
MySQL, Postpresql, etc.
< p>File-based ones are:
Access, SQLAnywhere, sqlite, interbase
What is a relational database
Introduction to relational databases Relational databases store data in the form of rows and columns to make it easier for the user to understand. This series of rows and columns is known as a table and a set of tables make up a database. Users use queries (Query) to retrieve data from the database. A Query is a SELECT statement used to specify rows and columns in a database. A relational database usually contains the following components: Client application (Client) Database server (Server) Database (Database) StructuredQueryLanguage (SQL) Client and Server side of the bridge, the Client with SQL to send requests to the Server side, the Server returns the Client’s request. Server returns the results requested by the Client. Now popular large-scale relational database IBMDB2, IBMUDB, Oracle, SQLServer, SyBase, Informix and so on. Relational databases are not the only advanced database model, and not at all the model with the best performance, but relational databases are indeed the most widely used and easiest to understand and use database model today. Most enterprise-level system databases use relational databases, and the concept of relational databases is fundamental to mastering database development, so the questions in this section have become one of the frequent questions in .NET interviews. Knowledge Points Involved Concepts of Relational Databases Benefits of Relational Databases Analyzing the Problems Concepts of Relational Databases The so-called relational database refers to a database that employs a relational model to organize data. The relational model was first proposed by Dr. E.F. Codd, a researcher at IBM, in 1970, and in the decades that followed, the concept of the relational model was fully developed and gradually became the dominant model of database architecture. Simply put, the relational model refers to a two-dimensional table model, and a relational database is a data organization composed of two-dimensional tables and the links between them. The following is a list of commonly used concepts in the relational model. Relationship: can be understood as a two-dimensional table, each relationship has a relationship name, which is commonly referred to as the table name. Tuple: can be understood as a row in a two-dimensional table, often referred to as a record in databases. Attribute: can be understood as a column in a two-dimensional table, often referred to as a field in the database. Field: the range of values of an attribute, that is, the limit of values of a column in the database. Keyword: a set of attributes that uniquely identifies a tuple. Often referred to as a primary key in databases, it consists of one or more columns. Relationship Schema: A description of a relationship in the format: relationship name (attribute 1, attribute 2, …, attribute N). It is often referred to as a table structure in databases. Advantages of Relational Databases Relational databases have the following advantages over other models of databases: Ease of Understanding: The two-dimensional table structure is a concept that is very close to the logical world, and the relational model is easier to understand compared to other models such as mesh and hierarchy. Easy to use: the common SQL language makes it very easy to operate relational databases, programmers and even data administrators can easily operate the database at the logical level without having to understand the underlying implementation. Easy to maintain: rich integrity (entity integrity, referential integrity and user-defined integrity) greatly reduces the probability of data redundancy and data inconsistency. In recent years, non-relational databases have developed rapidly in theory, such as: mesh model, object model, semi-structured model and so on. The mesh model has the advantage of higher performance, usually applied in systems with high performance requirements; object model conforms to the idea of object-oriented applications, which can be perfectly articulated with the program without the need for another intermediate conversion components, such as many of the current O\RMapping components; semi-structured model with the development of XML and the development of the wow now there are a lot of semi-structured database model. However, by virtue of its theoretical maturity, ease of use and the wide range of existing applications, relational databases are still the mainstream of system applications.
What are the non-relational databases
NoSQL, which is now popular,
What is a relational database?
A relational database is a database that uses a relational model to organize data. The relational model was first proposed by Dr. E.F. Codd, a researcher at IBM, in 1970. In the following decades, the concept of the relational model has been fully developed and has gradually become the dominant model of database architecture. Simply put, the relational model refers to a two-dimensional table model, and a relational database is a data organization composed of two-dimensional tables and the links between them. The following is a list of commonly used concepts in the relational model. Relationship: can be understood as a two-dimensional table, each relationship has a relationship name, which is commonly referred to as the table name. Tuple: can be understood as a row in a two-dimensional table, often referred to as a record in databases. Attribute: can be understood as a column in a two-dimensional table, often referred to as a field in the database. Field: the range of values of an attribute, that is, the limit of values of a column in the database. Keyword: a set of attributes that uniquely identifies a tuple. Often referred to as a primary key in databases, it consists of one or more columns. Relationship Schema: A description of a relationship in the format: relationship name (attribute 1, attribute 2, …, attribute N). Often referred to as a table structure in databases.
What kind of database information is available in relational databases
Lots of it. The relational ones are SQLServer, Sybase, Informix
mysql. and so on.
Real-time I know: LotusNotes. Including XML which can also be used as a real-time database.
What is a relational database?
Relational databases store data in the form of rows and columns so that it is easy for users to understand. This series of rows and columns is known as a table and a set of tables make up a database. Tables are related to each other with data records. The user uses a query (Query) to retrieve data from the database. A Query is a SELECT statement used to specify rows and columns in a database. A relational database usually contains the following components: Client application (Client) Database server (Server) StructuredQueryLanguage (SQL) A bridge between the Client and Server, where the Client uses SQL to send requests to the Server, and the Server returns the results requested by the Client. The Server returns the results requested by the Client. Now popular large-scale relational database IBMDB2, Oracle, SQLServer, SyBase, Informix, access, foxpro and so on.
What are the relational databases?
The current mainstream relational databases are Oracle, DB2, MicrosoftSQLServer, Mic nailosoft
Access, MySQL, etc.
What are the challenges faced by the traditional relational databases?
Challenge 1: Data sources are intricate
An abundant data source is a prerequisite for the development of big data industry. The total amount of digitized data resources in China is far lower than that of the United States and Europe, with the annual amount of new data being only 7% of that of the United States and 12% of that of Europe, of which the accumulation of data resources in the *** and manufacturing industries lags far behind that of foreign countries. As far as the existing limited data resources are concerned, there is also standardization, low accuracy, low completeness and low utilization value, which greatly reduces the value of the data
Challenge 2: Data Mining and Analysis Model Establishment
Being stepped into the era of big data, people are talking about big data, and it seems that this has evolved into a new trend trend. More than ever, data is rooted in every corner of our lives. We are trying to use data to solve problems, improve welfare, and enable new economic prosperity
Challenge 3: The trade-off between data openness and privacy
The premise of data application is data openness, which is already a consensus. Some professionals have pointed out that China’s population is the largest in the world, but in 2010 China’s newly stored data was 250 petabytes, which is only 60 percent of Japan’s and North America’s 7 percent. At present, some departments and organizations in China have a large amount of data but prefer not to use it themselves rather than provide it to the relevant departments for sharing, resulting in incomplete information or duplication of investment.In 2012, China’s data storage reached 64EB, of which 55% of the data requires a certain degree of protection, however, at present less than half of the data is protected!
What are the commonly used relational databases (What are the commonly used relational databases? What are the advantages of each?)
Nosql’s full name is NotOnlySql, a concept that has been around for a long time.Nosql refers to non-relational databases, and the ones we commonly use are relational databases. Just like our common mysql, oralce, sqlserver, etc., these databases are generally used to store important information, to deal with ordinary business is no problem. However, with the rapid development of the Internet, traditional relational databases are unable to cope with large-scale, large traffic and high concurrency. It was at this time that Nosql was born.
The above is the definition of NOSQL. The difference between Nosql and relational databases, here I explain a more important difference.
Storage format: relational databases are tabular, stored in rows and columns of tables. They are easily associated with each other collaborative storage, extraction of data is very convenient. And Nosql database is the opposite of it, he is combined together. They are usually stored in datasets, like documents, key-value pairs or graph structures. For example, for example, in the game inside the player’s backpack data, we all know that a game inside the props is a lot, and not sure when the player to get what props, this time if you want to store the data in the relational database, how to establish the table is a big problem, if you take all the props ID as the table header, then every subsequent increase in props, you need to modify this table. If your table structure is:
User ID|Props ID|Props Quantity|Props Special Attributes
Then you can imagine how huge this table will become with the increase of users. So this time we need a direct operation like the player object as the database, here is more representative of the mongo, through which we can see that the nosql database is more suitable for storing the structure of the data is not certain.
The examples above have illustrated the problem. In the modern age of internet everyone is looking to scale services across the line. This way the cost is minimized.
For the above relational database and NOSQL database difference in fact there are many. I believe that everyone in the use of will feel. The ones listed above are just the ones that I feel make the biggest difference.
So NOSQL is so good to use, is not all can use it, show is not so, NOSQL for aggregated query display is not his strong point. This time you need a relational database. I would suggest that, for the structure of the unified, should be stored in a relational database, for the structure of the non-uniform can be stored in the NOSQL database such as mongo. but this is not absolute, in the actual development of the project, according to their own business, carefully speculate on the most appropriate division of good.
The common relational databases are usually SQLServer, Mysql, Oracle and so on. The mainstream Nosql databases are Redis, Memcache, MongoDb. Most of the relational databases are paid and expensive, the cost is large, while Nosql databases are usually open source. In the Internet industry use mostly free MYSQL as well (snicker here).
In the actual project everyone’s project is how to choose? You can follow me, private message or leave a message in the comments section.
What are the commonly used relational databases?
1. Storage Engine: Data in MySQL is stored in files (or in memory) using a variety of different techniques. Each of these technologies uses different storage mechanisms, indexing techniques, locking levels, and ultimately provides a wide range of different features and capabilities. By choosing a different technology, you can gain additional speed or functionality that will improve the overall functionality of your application.
2. Index design: indexes and tables are generally created in different tablespaces to improve IO performance. Because the index will not take effect on the null value, so if a column has a null value and you want to create an index, then you can consider creating a combined index (colName,1).
3, sql optimizer (the core of the competition of commercial databases): due to the resource constraints of mobile devices, the embedded mobile database is generally integrated with the application system and exists as the front-end of the whole application system, while the data set it manages may be a subset or a copy of a subset of the data set in the back-end server.
4. Transaction management and concurrency control: In transaction processing, once an operation is abnormal, the entire transaction will restart, the database will return to the state before the transaction begins, and all operations on the database in the transaction will be canceled. If the transaction succeeds, all operations in the transaction are executed.
5, disaster recovery and disaster recovery technology: based on data synchronization and replication technology, through real-time synchronization of I/O, the server and database data from the source to the target end of the continuous capture (RPO tends to be close to 0, Note: RPO = the last backup and the occurrence of a disaster between the time of the business system is allowed to allow the maximum loss of data in the course of the disaster), and the entire self or manually create a data recovery point to ensure that the data occurred. Data Recovery Points to ensure that data is restored to the most recent point in time in the event of a data error.