hadoop relational database

Scenarios where relational databases cannot be used-reproduced:10 cases where the relational database is not available: things never to do with a relational db | Application Development-infoworld may be able to play a role in the direction of ordinary people.Translation of the main effect is as follows:1. Search: Even

Relational Database Terms and Definitions 1. Key: it is an important concept in a relational model. It is used to identify one or more columns of a row in a relational model. 2. Candidate Key: it is an attribute set that uniquely identifies a row in a table and does not contain any redundant attributes. That is, i

Infi-chu:http://www.cnblogs.com/Infi-chu/relational databaseRelational database is a database based on relational model, and the relational model is saved by a two-dimensional table, so the storage of relational

1. Concepts of relational databases A relational database refers to a database that uses a relational model to organize data. The relational model was developed by IBM researcher E. f. dr. codd first proposed that the concept of

Tags: delete a prim number href work otherwise HTTP keywordBasic concepts: keywords, primary keywords, candidate keywords, non-keywords If the value of a field or multiple fields uniquely identifies a record, the field or field group is called a keyword .If a keyword is used to identify the uniqueness of each record and is associated with other table implementations, it is called the primary key (primary key, primary key), or the main code .A keyword other than the primary keyword is called a ca

Tags: databaseThe database system is one kind of software, the database system naturally also has his own life cycle--the lifetime. Its lifetime begins with planning, until it is uninstalled. Its intermediate process is very complex, in order to realize the user's idea, the database personnel will abstract the real life data, then in the classification and the op

Tags: sqoop Import Database Source file JavaSqoop as a tool for data transmission, for Hadoop with the data transfer between the traditional database plays a bridge, so how to import and export data? First: Use MapReduce job to perform the import:( 1 ) Sqoop first check the table that will be imported1 , determines the primary key (if any), invokes the MapReduce

Design | data | database | Database design 1. Introduced Many people think that object-oriented concepts and relational databases are inconsistent and cannot be combined. In fact, quite the opposite! With flexibility, a relational database can provide an excellent set of im

Document directory 4) Check Integrity Constraint rules-how to execute Integrity Constraint rules in actual operations Introduction to database application development-basic concepts in relational databases are written before: relational databases are currently the most widely used databases. Understanding the basic concepts of

An important part of designing a relational database is dividing the data elements into related tables. Once you're ready to start working with the data, you can rely on relationships between tables to aggregate the data in a meaningful way. For example, unless you know which customer placed a particular order, the order information is useless. So far, you may have realized that you did not store customer a

Introduction to 1.mongodbMongoDB (http://www.mongodb.org/) is a high performance, open source (the generation of Earthquake army Daniel is studying MongoDB source code, we can go to see http://www.cnblogs.com/daizhj/), Mode Freedom ( Schema-free) is a document-based database that can be used in many scenarios to replace traditional relational databases or key/value (Key-value) storage methods. MongoDB uses

stage of the project (DBA is required for later optimization ). Based on the author's project experience, a developer proficient in OOP and ORM often designs more rational databases and better adapts to changes in requirements. if the reason is pursued, I guess it is because of database standardization, similar to some OO ideas (such as cohesion ). While DBA, the database designed has the advantage of bein

Index Understand the related tables. FOREIGN key JOIN and maintain referential integrity For some suggestions on joins, subquery VS. Linked table Query I found that there is a tutorial in the MySQL documentation, but the concept does not seem to mention, just tell you how (statement), did not tell you the cause and consequences (principle). Want to see a book with vivid explanations, such as the one that will give the various joins the VN diagram, and do not know how to fin

. The Minimum Redundancy must be achieved on the premise that the decomposed database can express all information of the original database. Its fundamental goal is to save storage space, avoid data inconsistency, improve the efficiency of relational operations, and meet application requirements. In fact, it is not necessarily required that all models reach bcnf.

After the concept of database was put forward, several data models appeared successively. There are three kinds of basic data models: Hierarchical model system, network model system, and relational model system. The relationship model proposed in the late 60 has the characteristics of simple and flexible data structure, easy to understand and strong mathematical foundation, and it has been popular since the

This paper mainly introduces the theoretical basis of relational database design which is closely related to the establishment of relational model (i.e. relational table structure), which is the basic knowledge of relational paradigm. The paradigm theory provides a theoretic