relational database diagram tool

With the development of relational databases, it has been nearly 40 years since the theory of relational models was proposed, the development of SQL query language, the establishment of performance tuning theory, and the maturity and prevalence of productization, IBM DB2, which claims to inherit this "conventional", has been in this history for 25 years. If the predecessor of DB2 SQL/DS is not included, ora

Abstract Yes: Workflow technology is one of the core technologies in office automation systems. Based on the features of the workflow in document flow, this paper analyzes the document flow data model established in the relational database, and provides the implementation method of the Document Flow System Based on this data model. 1. Introduction Office automation is a new office method that combines moder

. It can be seen that the external keyword represents the relationship between two relations, and the external keyword is also called the foreign key; 6. Database relationship diagram: the relational object in the database is used to describe the correspondence between tables in the

possible, so that space is small, but this requires a tradeoff between legibility and space occupancy. I have suggested that the author put the field name index, each of the field names in one byte, so you don't have to worry about how long the field name takes. But the author's concern is not unreasonable, this index method needs to be a result of each query to replace the index value with the original value, and then send to the client, this substitution is also very time-consuming. Now the r

integrity Used to set the value range of an attribute If you set the ethnic code and department code as foreign keys, the value must be 1 or 2 or NULL. Common relational databases:1. MySQL 2. SQL Server3.Oracle4. Sybase5.DB26 Informix7.Access III. install and start the Mysql database Mysqld.exe server program (if it is not started during installation, mysqld-install in cmd) Mysql.exe client program (

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

Tags: differentiating CTC identity sel paradigm Problem _id Third paradigm RelationshipThe sixth chapter of relational data theory This chapter explains the relationship normalization theory in detail, which is not only the important theoretical foundation of relational database but also the powerful tool of

a certain connection between them, such as a degree, it can have a master, PhD, bachelor and so on.The operation of the ER model is actually the operation of the ER model element, which is the operation between the entity, the relation and the attribute, and the purpose of the operation is to realize the requirement of the user while reducing the redundancy of the data.Transformation of 2 ER model to relational modelThe transformation from the ER mod

Tags: wait author href next explain tail time information problemPick self-Knowledge Liu Yan teacher detailed, clear answer for years of doubts. Liu ComfortLinks: https://www.zhihu.com/question/24696366/answer/29189700Source: Know Updated on 2015-1-9, answered@ Li Dezhu's problem ============ 2015-1-6 update, supplemented the BCNF interpretation ============ the majority of institutions in China Wang Shan "Database system Introduction" This textbook,

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

The next step is to explain each level of the paradigm, firstThe first paradigm (1NF). Conforms to the 1NF relationship (you can understand it as a data table.) The difference between "relationship" and "relationship pattern" is similar to the difference between "class" and "Object" in object-oriented programming. "Relationship" is an example of "relational pattern", you can understand "relationship" as a table with data, and "