Existing programmer training project, the project aims to provide the programmer with A technology of video teaching service, geared to the needs of users, including learners, instructor, administrator, system requirements are as follows: A, the user may be by email or phone number login system, to manage user information includes the user name, email address, phone number, learning interest, such as B, in order to provide accurate learning services, training camp will manage existing software development technology is divided into A number of directions, such as front-end developer, back-end development, mobile development, database, cloud computing and big data, such as C, under the direction of the technology and classified according to the technical management, such as HTML 5 and CSS 3, Node. Js, JavaScript, Java, C #, C/C + +, PHP, Android, MySQL, essentially A, D, online learning resources according to the curriculum organization, each course includes course name, course description, technical classification (A course can belong to multiple categories), number of learning, the difficulty level (course according to the difficulty is high, the low difficulty), price, instructor, E, each course is divided into chapters, each chapter is divided into several sections, each section has A video resources, learners can make comments or questions for the learning course, the logged in user can respond to the content of the comments or questions,

According to the task of database needs analysis and design, complete the following work:

(1) to complete the use case diagram and the drawing of system function structure,
(2) the analysis system of the entity, the relationship between the identification entity, e-r diagram drawing system, the use of PowerDesigner draw conceptual data model (CDM),
(3) the use of PowerDesigner, converting system conceptual model (CDM) into a physical data model (PDM),