What are the commonly used data files in the sales and collection subsystem?

What are the commonly used data files in the sales and collection subsystem? 1. Database definition: A database is an organized collection of a large amount of data stored in a computer for a long time. The data in the database is organized, described and stored according to a certain data model, with less redundancy, high data independence and easy expansion, which can be enjoyed by all kinds of users. 2. The development of database management technology has experienced three stages: manual management stage, file system stage and database system stage. 3.DBMS (Database Management System) is a layer of data management software located between users and operating systems. Main functions: 1, data definition function. 2. Organization, storage and management of data. 3. Data operation function. 4. Transaction management and execution management of database. 5. Establishment and maintenance of database. 6. Other functions. 4. What is a data model and its elements? (Design Question): Data model is a tool to abstract the real world in the database and a formal framework to provide information representation and operation means in the database. Generally speaking, a data model is a collection of strictly defined concepts. These concepts accurately describe the static characteristics, dynamic characteristics and integrity constraints of the system. Therefore, data model usually consists of three parts: data structure, data operation and integrity constraint. (1) data structure: it is a collection of object types studied and a description of the static characteristics of the system. (2) Data operation: refers to the set of operations allowed by instances (values) of various objects (types) in the database, including operations and related operation rules, and describes the dynamic characteristics of the system. (3) Data constraint: It is a set of integrity rules, which are the constraints and dependence rules of data and their relationships in a given data model, and are used to limit the state and state changes of the database that conform to the data model to ensure the correctness, validity and compatibility of the data. The most commonly used data models: hierarchical model, grid model, relational model, regional object model and object-relational model. 5. What are the commonly used data models (mainly logical models), what are their characteristics and data structures? A: Data models can be divided into two categories: the first category is conceptual model, also known as information model, which models data and information according to users' views and is mainly used for database design. The second category is logical model and physical model. Logical models mainly include hierarchical model, hierarchical model, relational model, object-oriented model and object-relational model. It models data from the perspective of computer system and is mainly used for the implementation of DBMS. Physical model is the lowest abstraction of data, which describes the representation and access methods of data in the system, as well as the storage and access methods on disk or tape, and is oriented to computer systems. The task of database management system is to realize physical model. Database designers should understand and choose physical vinegar, and ordinary users don't have to consider the details of physical level. The data structure characteristics of hierarchical data model are as follows: First, only one node has no parent node, and this node is called root node. Second, other nodes besides the root have one and only one parent node. Advantages: 1 The hierarchical data structure is relatively simple and clear. 2. The query efficiency of hierarchical database is high. 3. The hierarchical data model provides good integrity support. The main disadvantages are: 1. In the real world, many connections are non-hierarchical, such as many-to-many connections between nodes. 2. A node has multiple parent nodes, and so on. The hierarchical model is clumsy and can only be solved by introducing redundant data or establishing unnatural data structures. There are many restrictions on insert and delete operations, so the writing of applications is more complicated. 3. The query child node must go through the parent node. 4. Due to the tight structure, hierarchical commands tend to be stylized. It can be seen that the hierarchical model describes one-to-many departments naturally, intuitively and easily, which is the outstanding advantage of hierarchical database. Mesh model: function: 1. Multiple nodes without a parent node are allowed. 2. A node can have multiple parent nodes. The advantages of grid data model are: 1. It can describe the real world more directly, for example, a node can have multiple parent nodes. There can be multiple uplinks between nodes. 2. It has good performance and high access efficiency. The main disadvantages are: 1. The structure is complex, and with the expansion of the application environment, the structure of the database becomes more and more complex, which is not conducive to the end user to master. 2. DDL and DML of grid model are complicated and embedded in high-level languages, so it is not easy for users to master and use them. The relational data model has the following advantages: 1. Relational model is different from non-relational model, which is based on strict mathematical concepts. 2. The concept of relational model is simple. 3. The access path of relational model is transparent to users, so it has higher data independence, better security and confidentiality, and simplifies the work of programmers and the establishment of database development. The main disadvantage is that the query efficiency is often not as good as that of the non-relational data model, because the access path is clear. Therefore, in order to improve the performance, the database management system must optimize the user's query request. Therefore, it is more difficult to develop DBMS, but users don't have to consider the optimization technical details inside these systems. 6. What are the definitions of three-level architecture, external mode, mode and internal mode? Schema, also known as logical schema, is a description of the logical structure and characteristics of all data in the database, and it is a public data view for all users. External mode, also known as sub-mode or user mode, is a description of the logical structure and characteristics of regional data that database users can see and use, and a logical representation of data related to an application in the data view of database users. Internal schema, also known as storage schema, is a database with only one internal schema. It is a description of the physical structure and storage mode of data and a representation of data in the database. 7. Secondary image and secondary independence are called physical independence and logical independence. When the schema changes, the database administrator will change each external schema and the image of the schema accordingly, so that the external schema remains unchanged. The application program is written according to the external mode of data, so the application program does not need to be modified, which ensures the logical independence of data and programs, which is referred to as the logical independence of data for short. When the storage structure of the database changes, the database administrator can make corresponding changes to the schema and internal schema image to keep the schema unchanged, so that the application does not need to change. It ensures the physical independence of data and programs, referred to as the physical independence of data. 8. A database system generally consists of a database, a database management system (and its development tools), an application system and a database administrator. 9. Relationship integrity (entity integrity, referential integrity and user-defined integrity) consists of three parts, of which the first two parts are automatically supported by the system. What are the three main functions of DBMS integrity control subsystem? : Provides a mechanism for defining integrity constraints, provides a method for integrity checking, and handles breach of contract. Definition of 16. SQL structured query language is the standard language of relational database, and it is a universal and powerful relational database language. Classification (interactive and embedded) 17. The role of group by and having clauses. Concept of view: A view is a table derived from one or several basic tables. And related operations: define view, query view and update view. View updated operations: insert, delete and modify. 22. Definition of Database Normalization Method Function Dependence What is 1NF2NF3NFBCNF Definition: Relationships in a relational database must meet certain requirements, and what meets different requirements is different normalization. What meets the minimum requirements is called the first normalization, or 1NF for short. What meets further requirements in the first normalization is the second normalization, and so on. The relationship between various normalization is 5nf (4nf (bcnf (3nf (2nf (1nf)). 25. Several stages of database design, common methods and brief contents of each stage: six stages: demand analysis, conceptual structure design, Luo Zhi structure design, physical design, database implementation, database implementation and maintenance. 28. The concept of transaction? What are the basic attributes of a transaction? Mitrollback meaning: a transaction is a user-defined database operation sequence, which is an inseparable unit, either completed completely or not. Four characteristics: atomicity, consistency, isolation and persistence. Commit (all operations to commit the transaction) rollback (Rollback: There is some fault during the execution of the transaction, and the transaction cannot continue. All completed database operations in the transaction are cancelled and rolled back to the state at the beginning of the transaction. 29. What is the recoverability of a database system? The database management system has the function of restoring the database from an error state to a known correct state, which is the recoverability of the database system. Database failure types: internal transaction failure, system failure (soft failure), media failure (hard failure) and computer virus. 30. What problems may arise without concurrency control? The concurrent operation of multiple transactions on the database may lead to the destruction of the ACID characteristics of the transactions. How to solve (3): 1, lost revision 2, unrepeatable reading 3, reading "dirty" data. 3 1. Three-level blockade agreement? What problems can be solved? First-level blocking protocol: transaction T must add X lock to data R before modification, and will not be released until the end of the transaction. Transaction ending includes normal ending (commit) and abnormal ending (rollback). In the first-level blocking protocol, if the read data is not modified, there is no need to lock it, which can prevent the modification from being lost. Two-level blocking protocol: based on the first-level blocking protocol, transaction T is added. Before reading data R, an S lock must be added to data R, and then the S lock is released after reading. In the two-level blocking protocol, because the S lock can be released after reading the data, it cannot be guaranteed to be read repeatedly. Three-level blocking protocol: one-level blocking protocol plus transaction T must add S lock to data R before reading it, and will not be released until the end of the transaction. The three-level blocking protocol not only prevents the loss, modification and non-reading of "dirty" materials, but also further prevents the non-repetition of reading. The main differences between the above three-level protocols are: what operation needs to apply for blocking and when to release the lock. What three measures are generally taken? What about insertion? What about deleting? : 1, refused to execute (this operation is not allowed), 2, cascaded operation (when deleting or modifying one tuple of the referenced table leads to inconsistency with the referenced table, all tuples in the referenced table will be deleted or modified), 3, set to null value (when deleting or modifying one tuple of the referenced table leads to inconsistency, the corresponding properties of all tuples in the referenced table will be set. 38. What is the impact of views on database security? : 1, viewing can simplify users' operations, 2. eyesight enables users to view the same data from all angles, 3. Viewing provides a certain degree of logical independence for reconstructing the database, 4. Viewing can provide security protection for confidential data, and 5. Proper use of viewing can express queries more clearly. Database: A large collection of data stored in a computer, which is permanently stored, organized and enjoyed. Development stage of data management technology: 1. Manual management stage: data is not stored, data is managed, data is not enjoyed, and data is not independent. 2. File system stage: data can be stored for a long time and managed by the file system; Data * * * has poor enjoyment, great redundancy and poor data independence. 3. Database system stage: Database management system appears. Characteristics of database system: data structure (essential difference); Data * * * has high enjoyment, low redundancy and easy expansion; High data independence; The data is managed and controlled by the database management system. Database management system: 1. Definition: DBMS is a layer of data management software between users and operating system. 2. Function: data definition function; Organization, storage and management of data; Data operation function; Transaction management and execution management of database; Database establishment and maintenance functions; Communication function, data conversion function, mutual access and interoperability function. Database system: 1. Concept: DBS refers to the system after introducing the database into the computer system. 2. Composition: generally composed of database, database management system, application system and database administrator. 3. Classification: centralized, C/S, parallel and decentralized. Data model: 1. Definition: the abstraction of data characteristics in the real world. 2. Composition, three elements: data structure, data operation and data integrity constraint. The two data models are 1) conceptual model 2) logical model and physical model. Data structure: describes the components of the database and the links between objects, mainly describing the objects related to the types, contents and attributes of objects and the links between data. Common data model: 1. Hierarchical model, using tree structure to represent various entities and the relationship between entities. 2. Grid model allows multiple nodes to have no parent nodes, and allows a node to have multiple parent nodes. 3. Relational model, including single data structure

In sales management, there should be basic information about customers' purchases, as well as records of products purchased and customer payment plans.

According to the collection plan, the accounts receivable subsystem automatically lists the funds that need to be collected in a certain period (time range).

Please list the operational amplifier circuits (including: amplification, addition and subtraction, integration, differentiation, exponent, etc.). ) Analog circuit modules commonly used in electronic systems; Feedback amplifier circuit (introducing feedback concept); Power amplifier circuit (high power output drive circuit); Signal generating circuit (including various waveform generating circuits, square wave triangular wave sine wave); Signal processing and conversion circuit (including waveform shaping, waveform conversion, comparator circuit, modulation and demodulation, voltage-current conversion, voltage-frequency conversion, etc. ); Power supply voltage stabilizing circuit (including various power supply circuits, such as linear voltage stabilizing power supply, switching power supply, constant current source, etc.). ). There are many kinds of simulation classes. There are too many digital circuits: gate circuits, encoders, decoders, counters, frequency dividers, buffers, drivers, triggers, operators, registers, latches, data selectors, analog switches, phase-locked loops, and timers; Too many (microprocessors, memory, A/D, D/A and other microcomputers). Learn slowly by yourself.

Data commonly used in statistics? Skewness and kurtosis, the formula is a bit troublesome to write by yourself, so you can search online yourself.

How to COPY data files from ASM to operating system can use cp function of *** cmd command or copy function of RMAN.

Askmaclean Oracle Bone Inscriptions

Hello, if your Oracle database system uses ASM automatic storage management, have you ever thought about peeking at the data files in ASM? ASM is a black box. You can't see the data files in it through the operating system, and you can't copy or delete them through operating system commands. Here is a simple and applicable method to copy data files in ASM. A tool that everyone is familiar with, that is: Rman!

As we all know, when migrating data across platforms, we will encounter the problem of byte storage order in the operating system. We usually use Rman's convert command to convert the byte order of tablespaces or data files. Similarly, the following also introduces how to copy data files from ASM through Rman's convert;

Seeing this data file in a *** cmd, I want to copy the data file named seven (note the path): 536001

ASMCMD & gt displays the current working directory.

+Seven/Production/Data Files

ASMCMD & gt Limit Switch

For example: 26768+09799583667

Seven o'clock. 36860.88878888686

sysaux . 257.8 19799 14 1

system . 256.8 19799 14 1

undotbs 1.258 . 6438+09799 143

undotbs 2 . 58687

Users. 28638+09799638+043

ASMCMD & gt

Transform under Rman by the following command:

Convert data file

Seven/products/data files/seven. 18660.7886868686 17

Database file name conversion

+seven/prod/datafile '，'/home/Oracle '；

This command is very simple. The keyword db_file_name_convert is required for the conversion of single data to specify the path where the data file is located before and after the conversion. In this experiment, the data file named SEVEN.320.822828439 was converted from the original path +seven/prod/datafile to the later /home/oracle directory, and the file name remained unchanged.

The output is as follows, showing the completion of the conversion:

Backup started on 07-AUG- 13.

Use ORA_DISK_ 1 channel.

Channel ORA_DISK_ 1: Start data file conversion.

Input file name =+seven/product/data file/seven. 59660 . 68686868666

The converted data file =/home/Oracle/seven. 49660.68868688666

Channel ORA_DISK_ 1: data file conversion completed, time taken: 00:00:05.

The backup was completed on 07-AUG- 13.

All right! After the conversion is completed, you can go to the /home/oracle directory to see if there is this data file;

[Oracle @ ora 1 ~]$ ls-al seven . 5866867667

-rw-r- 1 Oracle oinstall 52436992 Aug 7 16:4 1 seven . 5960607

[oracle@ora 1 ~]$