nosql databases vs relational databases

Key-Value DatabaseApplicable casesNow let's talk about a few things that are appropriate for using key-value databases.1 Memory-Touch Session informationTypically, each network session is unique, so the session ID values assigned to them are also different. If the application originally wanted to put the session ID on disk or in a relational database, it would benefit a lot after migrating it to a key-value

Currently, all workflow systems require the support of relational databases. A workflow system is required, especially when the workflow engine is started during running, you need to use a database to run the process instance and record the status value of the process. It can be said that the workflow engine has a very close relationship with the database. without the support of the database, the workflow c

ensure uniqueness of each record. These identities or "keys" can be used to connect information that exists in different tables. For example, you can specify a unique person number key value for each person in the people table, and use the same key value in the corresponding field in the Address table. This allows you to associate each person with his or her address by matching the value of the "Person number" field in the two tables. The relational

value. The values for each city and state are entered only once in their respective tables. ZipCode and City tables require foreign key fields to accommodate these relationships:Zip codeZip codeCity. City One-to-manyCityCity (primary key)State. One-to-many statesStateStatus (primary key)From one point to nine pointsFinally, you have nine tables: book, author, category, publisher, zip code, city, state, book author, and book category. Figure One displays a graphical representation of the sample

HIVE_HOME =/home/hadoop/hive-0.8.1At this time, we can perform the test. We primarily use hive for interaction. Actually, we submit data from a relational database to hive and save it to HDFS for big data computing. Sqoop mainly includes the following commands or functions. Codegen Import a table definition into Hive eval Evaluate a SQL statement and display the results export Export an HDFS directory to a database table help List available commands

Today, a business requirement involves the third paradigm. Sort out the concepts here to facilitate future queries: 1. 1nf) In any relational database, the first paradigm (1nf) is the basic requirement for the relational model. databases that do not meet the first paradigm (1nf) are not relational

A solution to the database sub-table of relational databasesWhen a relational database library or a single table reaches a certain level of data, a performance bottleneck occurs for a single node. The usual practice is to consider the sub-database table.Why do you want to divide?The Sub-Library reduces the load of the single point machine and the table, which improves the efficiency of the data operation, e

data with high physical independence. It defines the correspondence between the global logical structure of the database and the storage structure. The image definitionUsually included in the pattern description. When the storage of the database is over, the DBA will change the pattern/internal mode image accordingly so that the pattern remains unchanged. mode unchanged, withApplications that do not have direct contact with the schema will not change. Therefore, the mode/internal mode image fun

The construction of the database must follow certain rules. In a relational database, this rule is a paradigm. A paradigm is a collection of relational patterns that conform to a certain level. Relationships in relational databases must meet certain requirements, that is, to satisfy different paradigms. There are six t

[Csdn latest news in April 30] A few months ago, Microsoft launched the cloud-based SQL data service (SDS), but it was criticized for its lack of strong support for enterprise-level applications. Microsoft is actively promoting a new measure to replace SDS by establishing a pure Relational Data Model running on the cloud computing platform. Microsoft took this surprise one week before the mix09 meeting in Las Vegas last month. The irony is that the m

Tree-structure data is a solution for distributed applications based on relational databases. The question is very big. To put it simple, it is actually that tree-structure data is often used in distributed applications, such: organization structure, bill of materials, etc. However, the data in these tree structures must be accessed Based on Relational Data. Gene

Design paradigm of relational databases and database design paradigm 1. 1NF)The first paradigm is the basis of the second and third paradigm and the most basic paradigm. databases that do not meet the first paradigm are not relational databases.Guiding principles of the first paradigm:1) Each attribute of a Data Group

to perform cross-Table operations.And now. net 3.5 (in.. Net 3.0). Through LINQ to SQL, we can also automatically generate relevant code and access and operate databases in a fully object-oriented manner. Cross-Table operations are also easy, the development efficiency has been greatly improved, and it can be said that it has reached the peak of data access methods.From the evolution of the above data access technology, we can see that Microsoft is d

When dealing with Microsoft SQL Server 2005 Analysis Services (SSAs) Multidimensional datasets and dimensions, you can use existing relational databases to design multidimensional datasets and dimensions. You can also design multidimensional datasets and dimensions first, then, use the architecture generation Wizard to generate the architecture based on the multi-dimensional dataset and dimension you design

When you save an XML document in a relational database, you must have encountered many problems with methodological reasons, especially for a large number of documents. This article will present specific problems related to a large number of XML documents, and then give a solution to these problems. Potential problems with a very large number of documents What makes an XML document very large? One of the signs that an XML document becomes huge is that

Number 9 NVARCHAR2 VARCHAR (20) NVARCHAR2 10 RAW VARCHAR (20) 11 TIMESTAMP UNKNOWN Datetime 12 TIMESTAMP (6) with LOCAL time ZONE Tinytext Tinytext 13 TIMESTAMP (6) with time ZONE Tinytext Tinytext 14 Clob Mediumtext Mediumtext 15 LONG Tinytext Tinytext 16 NCLOB

) IsolationThe so-called independence refers to the concurrent transactions do not affect each other, if one transaction to access the data is being modified by another transaction, as long as another transaction is not committed, the data it accesses is not affected by uncommitted transactions.For example, there is a transaction from a to 100 yuan to the B account, in the case of the transaction is not completed, if at this time B query their own account, is not see the new increase of 100 yuan

relational databases Follow acid rulesTransactions are transaction in English, similar to real-world transactions, and have the following four features:1, A (atomicity) atomicityAtomicity is easy to understand, that is, all operations in a transaction are either done or not, and the transaction succeeds because all operations in the transaction are successful, and as long as one operation fails, the entire

This article is translated from Coding-geek article: How does a relational the database work.Original link: http://coding-geek.com/how-databases-work/#Buffer-replacement_strategiesThis article translates the following chapters: One, Array, Tree and Hash tableThrough the previous chapters, we have already understood the concept of time complexity and merge ordering, and I will introduce three data stru

Relational databases use keys to construct relationships between data. Too many indirect relationships lead to complicated logic. Today, I encountered this situation when designing a public opinion monitoring system. For data output flexibility, the database is designed centered on customers and keywords. However, in order to increase the Cluster load, data crawling is designed to be distributed, which cr