First, many people think that database programming is a tempting work, which comes from the huge market demand for database applications. Computer applications include scientific computing, data processing and process control three major areas, and data processing is a region in which the largest proportion is, including the current most popular client / server mode (C / S), Internet mode (B / S) Application can be classified from this application from a broad sense. It is because the market demand is huge, the database programming prospect is optimistic, you intentionally enter your programming hall, is it a bit heart? Second, database application and programming principle 1. The development of the database application is developed on the basis of the file system, and has experienced three phases of the hierarchical database-mesh database-relational database. Since the relational database uses people's two-dimensional table to organize data, it has developed rapidly, and has become the mainstream of database products. The database knowledge we introduced here refers to the relational database. 2. Basic Concept Database (Database, DB) is stored in a computer memory in a certain organization, and the database is independent of the program. The so-called relational database is to represent a collection of data as a table, define a database of the structure by establishing a relationship between simple tables. The Database Management System (DBMS) is a software system for managing databases that provides users with methods and commands for describing databases, manipulating databases, and maintenance databases, and can automatically control the security of the database and data is complete. Database, which is now Oracle, Sybase, Microsoft SQL Server is a database management system. Database System (DBS) is a computer system with management database features, including applications, database (DB), database management system (DBMS), and database management (DBA). Our database programming today refers to the development of the database system, which is to manage the database, and implement data valid management. We intuitively understand the architecture of the database programming as follows: Of course, database managers are generally for large database applications, small database applications do not have a dedicated database administrator. Some readers may mistakenly think that database programming is to write database applications, in fact, the database design, such as preparing a salary management system, how to organize personnel information, wage information, design data structure, and work should be considered by database programming . DBMS is the database's own function, do not need us to consider, we only have to deal with their interfaces (such as contemporary development tools). ODBC is available to connect to the database). Regardless of the physical storage method in the database file, it can be seen as a row and column, similar to the rows and columns of the spreadsheet Excel. In the relational database, the line is called records, and the column is called a field. Here is an example of an employee wage form. Employee Name Age Title Work Time Basic Salary 1 Qiaofang 32 Senior Engineer 1990/07/01 1000.007 Zhang Wuji 25 Engineer 1997/08/01 800.00 We can see that each line of this table describes the information of a company's specific employee, called For a record; each record contains the same type and quantity field. From this table we define the following definition: Table is a logical group, such as the company's employee table, by row. Each column in the field database table is called a field. The table structure is defined by the various fields therebetween, each field describes one of its attribute values.
Fields can contain various characters, numbers, or even graphics (such as photos that save employees). Record the row stored in the table, called record. Any two records in the same data sheet cannot be exactly the same. The key button is a (or more) fields in the table, and the key can be unique or unique. The unique key can be specified as the primary key to uniquely identify the table. For example, in the employee table, the employee number is the primary key of the table, because it uniquely identifies an employee (here we can't use the name to make a primary key, because the name cannot be uniquely identified, may have a rename). The relationship is the connection between the table and there. The database can be composed of multiple tables, and the tables can be associated with each other in different ways. For example, the employee database can also have a table containing other information of an employee, which is related to the employee table. Third, the SQL language tells the database programming, you can't not mention the SQL language. The English full name of the SQL language is Structured Query Language, meaning structured query language. The main function of the SQL language is to establish a contact with various databases, communicate, to perform a wide variety of operations, such as updating data in the database, extract data from the database. SQL has been used as a standard language of the ANSI (National Standards Association) and the International Standardization Organization (ISO) as a relational database management system. Currently, most popular relational database management systems, such as Oracle, Sybase, Microsoft SQL Server, DB2, etc., follow SQL language standards. Workers must have a good fault, must first make a tool, the next job is to choose a better database development tool. 4. Comparison of several database development tools currently includes some proprietary database vendors to provide database programming tools, such as Oracle's developer 2000, Sybase's Power , but more popular or Delphi, VB, PowerBuilder, etc. The development tools have their own strengths and advantages. If VB uses a Basic language, it is easy to learn, and it has strong combination with Microsoft products; Delphi has excellent component technology, compiling speed, high-oriented Pascal language has high compilation efficiency and intuitive syntax PowerBuilder has a strong data window technology as Sybase patents, providing a private interface with a large database. VFP also has a large number of users in China, but Microsoft announces no longer launching new versions from VFP6, and many previous FOX programmers have turned to other development tools. For beginners, you can choose according to your needs. I will introduce you to the database development tool PowerBuilder, which is a good hand of the database programming "short". V. Powerbuilder Database Programming Introduction PowerBuilder (hereinafter referred to as PB) is an object-oriented graphical interactive development tool for application development applications developed by Sybase's wholly-owned subsidiary. PB is increasingly favored by programmers with its simple and efficient integrated development environment, powerful data window technology, almost omnipotent database access capabilities and friendly user interface. PB6.5 is currently the most version of the application, PB7 has been launched for a long time, but it seems that it is not stable enough, and PB8 is also developed. It is a product worthy of our expectations. We use PB6.5 as an example for example. PB database applications typically include three parts: user programs, database engines, and databases. The database engine is the interface provided by PB, with a database engine, we can't understand the technical details of accessing the database, and put energy on the database design and user program.
