Tutorials to .com

Tutorials to .com » Database » Foxpro » VFP Chapter Essentials basic knowledge of database systems

VFP Chapter Essentials basic knowledge of database systems

Print View , by: iSee ,Total views: 25 ,Word Count: 2788 ,Date: Sat, 18 Apr 2009 Time: 4:07 PM

1.1 database system

1. Data Processing

Data:

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.

Data processing:

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 Language:

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.

Components:

Database

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

VFP Chapter Essentials basic knowledge of database systems

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
Database menu
Class Menu

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

Project:

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.

Project Manager:

VFP Chapter Essentials basic knowledge of database systems

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


FoxPro Tutorial Articles


Can't Find What You're Looking For?


Rating: Not yet rated

Comments

No comments posted.