VFP Chapter Essentials basic knowledge of database systems
1. Data Processing
The fact is, concepts or instructions of a particular form of expression can be used manually or automated devices to communicate, translate or convert for reprocessing. It includes two types: one is to take part in the number of computing numerical data; a class is not involved in computing the number of non-numerical data, such as text, pictures, sounds, images and other activities.
Of various types of data collection, storage, sorting, calculating, processing, retrieval and transmission process.
Include: the collection of raw data, data conversion, data entry, data processing, data output.
2. database System
(1) database (DataBase)
Definition: a certain form of organization is stored in a computer storage medium on the interrelated collection of data.
Characteristics: with a minimum of redundancy, with data independence, data sharing, safe, reliable, confidential performance
(2) database management system (DataBase Management System)
Definition: is the manipulation and management of database system software. Visual foxpro is a relational database management system.
Data definition language (DDL): used to create the required database.
Data Manipulation Language (DML): used to query the database and maintain the operation.
Relational database using the standard language is the Structured Query Language (Structured Query Language, SQL).
(3) database (DataBase System)
Definition: is a database application based on computer systems.
Hardware (computer hardware)
software (database management system, operating system)
User (application programmer, end-user, database administrator)
Category: hierarchical databases, network databases, relational database
Sub-generation: the first generation of non-relational database systems, at the end of the 60's come out, including the level and type mesh.
Second-generation relational database system (RDBS), 70 came in the mid.
The third generation of the object - relational database system (ORDBS, OOBDS), 80 since the mid.
The above-mentioned link between the three concepts: In the database system through the database management system to create and use databases.
3. Relational model
Three areas: the real world things → (object, nature)
The concept of the world → entity (object, attribute)
Data World → data (records, fields)
Solid Model: things that reflect the physical contact.
Data model: a model to describe the data entities.
The classification of data models: hierarchical model (using the tree structure)
Network model (using undirected graph structure)
Relational model (using two-dimensional table structure)
The nature of the relational model:
The number of records in two-dimensional table of data to increase with the change, but the fields are relatively fixed; two-dimensional table for each column are the only field names; two-dimensional table, there does not allow two lines of identical two-dimensional form of the order of Bank of China, listed in arbitrary order can be exchanged.
Two-dimensional table of the main keyword: super-keywords: can only identify a record or a combination of several listed
Candidate keywords: The most concise super keyword
Main keywords: a keyword candidate
External keyword: When A table of the main keywords to be included when the table B, then A table of the main keyword for the B form of external keyword.
4. Microcomputer relational database systems
Relational database: that is, under the table, records and the relationship between field organizations and a visit to a database.
|Name||Operating environment||Company Name||Published|
|dBASE, dBASE Ⅱ, dBASE Ⅲ, dBASE Ⅲ PLUS, dBASE||DOS||Ashton-Tate|
|FoxBASE 1.0||DOS||Fox Software||1987.2|
|FoxBASE + (2.00/2.10)||DOS||Fox Software||87.7/88.7|
|FoxPro 1.0||DOS||Fox Software||1989|
|FoxPro 2.0||DOS||Fox Software||1991|
|FoxPro 2.5||DOS, WINDOWS 3.x||Microsoft||1993.1|
|FoxPro 2.6||DOS, Windows 3.x||Microsoft||1994|
|Visual FoxPro 3.0||Windows 3.X||Microsoft||1996.1|
|Visual FoxPro 5.0||Windows 95||Microsoft||1997.2|
|Visual FoxPro 6.0||Windows 98||Microsoft||1998.1|
Outlined in 1.2 Visual FoxPro 6.0
1. VFP6.0 characteristics
Perfected the concept of relational database using the Rushmore technology, the introduction of a SQL command; supports a wide range of data exchange format; visualization using object-oriented programming approach; provides a fully functional integrated development environment and rich.
2. VFP6.0 user interface
Interface elements: the title bar, main menu bar, toolbar, main window, command window, the status bar
System Tools List
|A variety of menu||A variety of toolbar||Various window||A variety of designer||Various generators||Various Wizard|
|File menu||Common Toolbar||Command window||Database Designer||Text Box Generator||Table Wizard|
|Edit menu||Form Control Toolbar||Browser window||Table Designer||Combo Box Generator||Crosstab Wizard|
|Show menu||Layout Toolbar||Code window||Form Designer||Order group generator||Query Wizard|
|Format menu||Debug window||Menu Designer||Edit box generator||Local View Wizard|
|Tools menu||Print Preview toolbar||Edit Window||Report Designer||Generator expressions||Form Wizard|
|Menu||Statement Control Toolbar||Show window||Designer labels||Form Generator||One-to-many form wizard|
|Window menu||Query Designer Toolbar||Tracking Window||Class Designer||Form Generator||Report Wizard|
|Help menu||Form Designer Toolbar||Properties window||Connection Designer||List Box Builder||One-to-many Report Wizard|
|Menu Menu||Report Designer toolbar||General field window||Query and view designer||Referential integrity Generator||Tags Wizard|
|Data Environment menu||Database Designer toolbar||Remote View Wizard|
|Form menu||project Manager window||Data Environment Designer||Generator automatically format||mail Merge Wizard|
|Menu item||Import Wizard|
|Query menu||Options Group Generator||Graphics Wizard|
|Statements menu||PivotTable Wizard|
|Table menu||Packet / Total Report Wizard|
3. vfp 6.0 approach
(1) menu operation
According to the operational requirements from the menu select the appropriate command (with similar WORD). Once for each menu command, the command window usually shows the corresponding menu command and contents.
Use the Tools menu in the Wizard can easily complete routine tasks.
(2) command interactively
To be carried out in accordance with the operation, the use of man-machine dialogue in the command window one by one by the formal requirements needed to enter an order, press enter after the implementation of the machine one by one.
(3) procedures for implementation
First in the program editor window procedure for END, and then choose from the implementation of procedures, or from a command window, type DO command, so that the implementation machinery.
4. VFP 6.0 common file types
VFP 6.0 common file extensions and their associated file types
|Extension||File type||Extension||File type|
|. app||application generated||. frx||Statements|
|. exe||Executable program||. frt||Statements Remarks|
|. pjx||Item||. lbx||Tags|
|. pjt||Project Notes||. lbt||Tags Remarks|
|. dbc||Database||. prg||Procedures|
|. dct||Database Remarks||. fxp||Procedures compiled|
|. dcx||Database Index||. err||Compile Error|
|. dbf||Table||. mnx||Menu|
|. fpt||Table Remarks||. mnt||Menu Remarks|
|. cdx||Composite Index||. mpr||Procedures generated menu|
|. idx||Single index||. mpx||Compiled menu program|
|. qpr||Inquiries generated by the procedure||. vcx||Video Library|
|. qpx||Compiled query program||. vct||Visual Class Library Notes|
|. scx||Form||. txt||Text|
|. sct||Remarks Form||. bak||Backup files|
5. To create a document
New types of documents, can be used to provide the corresponding tools in order to enhance efficiency. New documents available, and guide the design.
1.3 Project Manager
1. Project Management Introduction
Is a document used to track the creation of applications for all required procedures, forms, menus, libraries, reports, labels, queries and a number of other types of files.
VFP applications is to develop a tool to generate a project file, project file extension. PJX, the extension project Remarks:. PJT.
Project Manager window consists of:
Data from 6 major categories of items (all, data, documents, category, code, other), and 10 command buttons (New, add, modify, view, closed, open, preview, run, remove, and even for) the composition of .
Note: bold italic command button that the user selected in accordance with the corresponding objects appear different.
Menu item: the 13 sub-menu (part of the project manager in the same command button).
Project management functions: organization and management of all system and application of the various types of documents.
2. The creation of project documents
Way to use the menu:
Open the File menu → New → Project → file → new projects are given the appropriate file name and saved into the project manager → → → the development and application of the system to close the window after the completion of withdrawal.
Way to use the command:
Syntax: CREATE PROJECT <project file name>
Function: open browser window to carry out project management application system.
3. To amend the project documents
Way to use the menu:
Open the File menu → Open → find the project documents and to determine access to the project manager → → → modify applications to close the window after the completion of withdrawal.
Way to use the command:
Syntax: MODIFY PROJECT <project file name>
Function: open browser window to carry out project management application system changes.
4.'s Use of project management
Project management can be used to create, open, browse, modify and run all the VFP file the form, statements, labels, menus, procedures and so on. In particular, it can even use it for projects (to track changes in these documents, including the correlation between them, to use and connectivity, to ensure that the integrity of the quote, and to join since the last even after the update for some components) , the application (the extension. APP, in the circumstances VFP) and the executable file (extension. EXE, to the environment from the implementation of VFP).
1.4 VFP 6.0 a number of rules
1. VFP6.0 naming rules:
Only letters, underscores and numbers.
The use of letters or an underscore for the beginning of the name.
Name can be 1-128 characters, but the freedom of the table field names and index marking a maximum of 10 characters.
Visual FoxPro to avoid the use of reserved words.
File naming convention to follow the operating system.
2. The written orders and rules of clause
(1) to the beginning of the command verbs;
(2) to use a space between the separated parts;
(3) order, clause, function names can be abbreviated to four characters before, and large, lowercase equivalent;
(4) Write a command line only, the total length of not more than 8192 characters, when more than the width of the screen to continue the site ";";
(5) variable names, field names and file names should be avoided with the command verb, keyword, or function of the same name to avoid confusion when running.
(6) command symbol format agreed:
Order of , |, ..., "> symbols are not the syntax of the command element of itself, can not be used as they stood when the input,
Of which:  indicates optional, according to the specific circumstances of deciding whether to choose
| That can only be selected on both sides of the part of one of
... That can have any similar parameters, the parameters separated by commas
<> That the contents of which should be the actual name or parameters into the
3. Work order of common errors
(1) command verb wrong
(2) The format does not meet the requirements
Punctuation is not (must use English punctuation)
Lack of necessary space, or should not have added space
Inconsistent data types, it is necessary to pay attention to character, numeric, date-based, logical data format of writing
(3) could not open the required documents: There is no drive letter and enter the correct path or file name of mismatched
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