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This article mainly introduces the meaning of sql in the database, the article is very detailed, has a certain reference value, interested friends must read it!

Brief introduction

SQL (Structured Query Language) is a database language with many functions such as data manipulation and data definition. This language has interactive characteristics and can provide great convenience for users. The database management system should make full use of SQL language to improve the work quality and efficiency of computer application systems. SQL language can not only be used in the terminal independently, but also can be used as a sub-language to provide effective help for other programming. In this program application, SQL can optimize the program function together with other programming languages, and then provide users with more and more comprehensive information.

SQL Server database includes two sub-databases, Microsoft SQL Server and Sybase SQL Server. Whether the database can run normally or not is directly related to the security of the whole computer system.

In the era of big data, the data type and scale of database system are constantly expanding, which brings some challenges to database management. In social production and life, the scope of application of database is gradually increasing, and improving the efficiency of database development and application is the key to ensure the efficient operation of social production and life in our country.

As a set of operating commands, SQL is widely welcomed by people in the industry because of its rich functions, and has become a guarantee to improve the efficiency of database operation. The application of SQL Server database can effectively improve the speed of data request and return, and effectively deal with complex tasks, which is the key to improve work efficiency.

Because SQL Servers database management system has high data management performance, because of its superior performance, a wide range of applications, a large number of applications in the server and client architecture. The nature of SQL Servers database is mainly reflected in the following aspects: system throughput, response time and parallel processing ability, the speed of sending request server response, and the speed of switching between different screens, and so on.

Advantages

1) non-procedural language

2) uniform language

3) it is the common language of all relational databases.

System

The data architecture of SQL database is basically a three-tier structure, but the terminology used is different from the traditional relational model terminology. In SQL, relational schemas (schemas) are called "base table"; storage schemas (inner schemas) are called "storage files" (stored file); subschemas (external schemas) are called "views" (view); tuples are called "rows" (rows); and attributes are called "column".

Composition

Before formally learning the SQL language, let's first have a basic understanding of the SQL language and introduce the composition of the SQL language:

1. An SQL database is a collection of tables (Table) defined by one or more SQL schemas.

two。 An SQL table consists of a rowset, a row is a sequence of columns (a collection), and each column corresponds to a row with a data item.

3. A table is either a base table or a view. A base table is a table that is actually stored in a database, while a view is a definition of a table that consists of several basic tables or other views.

4. A basic table can store files across one or more files, and a storage file can hold one or more basic tables. Each storage file corresponds to a physical file on the external storage.

5. Users can use SQL statements to query views and basic tables and other operations. From the user's point of view, the view and the basic table are the same, there is no difference, they are both relationships (tables).

6.SQL users can be applications or end users. SQL statements can be embedded in programs in the host language, such as FORTRAN,COBOL,PASCAL,PL/I,C and Ada. SQL users can also be used as independent user interfaces for end users in an interactive environment.

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