What does sql refer to?

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Introduction

##　SQL (Structured Query Language) is a database language with multiple functions such as data manipulation and data definition. This language has interactive characteristics and can To provide users with great convenience, the database management system should make full use of the SQL language to improve the work quality and efficiency of the computer application system. The SQL language can not only be used independently in terminals, but can also be used as a sub-language to effectively assist other programming. In this program application, SQL can work with other programming languages ​​to optimize program functions, thereby providing users with more and more comprehensive information.

The SQL Server database includes two sub-databases, Microsoft SQL Server and Sybase SQL Server. Whether the database can operate normally is directly related to the operation security of the entire computer system.

In the era of big data, the data types and scale of database systems are constantly expanding, which brings certain challenges to database management. In social production and life, the application scope of databases is gradually increasing, and improving the efficiency of database development and application is the key to ensuring the efficient operation of my country's social production and life.

SQL, as a operation command set, is widely welcomed by people in the industry for its rich functions and has become a guarantee for improving the efficiency of database operations. The application of SQL Server database can effectively improve the speed of data request and return, effectively handle the processing of complex tasks, and is the key to improving work efficiency.

Since the SQL Servers database management system has high data management performance, its application range is very wide due to its superior performance, and it is widely used in server and client architectures. The nature of SQL Servers database is mainly reflected in the following aspects: system throughput, response time and parallel processing capabilities, the speed of server response when issuing requests, and the speed of switching between different screens, etc.

Advantages

　1) Non-procedural language

##　2 ) Unified language

　3) It is the common language of all relational databases

System

The data architecture of SQL database is basically a three-level structure, but the terminology used is different from the traditional relational model terminology. In SQL, the relational schema (schema) is called a "base table"; the storage schema (inner schema) is called a "stored file"; the subschema (external schema) is called a "view" ); tuples are called "rows"; attributes are called "columns".

Composition

Before formally learning SQL language, let us first have a basic understanding of SQL language. Introduction Let’s look at the composition of the SQL language:

1. A SQL database is a collection of tables, which is defined by one or more SQL schemas.

2. A SQL table is composed of a row set. A row is a sequence (set) of columns, and each column and row correspond to a data item.

　3. A table is either a basic table or a view. The basic table is the table actually stored in the database, and the view is the definition of a table composed of several basic tables or other views.

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

5. Users can use SQL statements to query views and basic tables. From the user's perspective, views and basic tables are the same, there is no difference, they are all relationships (tables).

　6.SQL users can be applications or end users. SQL statements can be embedded in host language programs. Host languages ​​include FORTRAN, COBOL, PASCAL, PL/I, C and Ada languages, etc. The SQL user can also be used as a separate user interface for end users in an interactive environment.

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