Advance understanding of software development (25) database Introduction

Database is a universal and comprehensive data set, which can be shared by various users with minimal redundancy and high data and program independence. At present, the international leading large-scale database management system has Oracle, SQL SERVER, SYBASE, Informix and Ingres and so on.

The common programming language in the database is the SQL language, which can be divided into four parts according to its function:

(1) Data definition language (LANGUAGE,DDL), which is used to define, undo, and modify data patterns.

(2) Query Language (data query LANGUAGE,DQL) for querying data.

(3) Data manipulation language (manipulation language,dml) for adding, deleting and modifying data.

(4) Data Control Language (LANGUAGE,DCL) for the control of data access rights.

Among them, the data definition language includes create, DROP, and ALTER statements, and the data query language includes the SELECT statement, the data manipulation language includes update, delete, and INSERT statements, and the Data Control language includes the GRANT statement.

In the database, in addition to the above four kinds of SQL language, also involves the concepts of table, index, stored procedure and transaction, they are also indispensable in actual programming.

In real software development projects, dealing with a variety of databases is a commonplace. In the daily work of the author, there are two types of databases that are frequently used: Sybase database and Oracle database.

(1) Sybase database

Sybase launched its Sybase database product in 1987. This is a database based on client/server architecture, which is widely used in communication software products because of its open and high performance characteristics.

When we run Sybase database scripts, we use a client software called Sybase, which is shown in Figure 1.

Figure 1 "Sybase the" Client software interface

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