This section describes the database related to technology, including database system, SQL language and database access technology.
database system
DBMS (Database Management System, DBMS) software is located for manipulating and managing the database between the operating system and the user, according to certain scientific data organizing and storing data models, while providing for efficient data acquisition and maintenance.
DBMS main features include the following aspects.
1) Data Definition Function
Data definition language provided by the DBMS (Data Definition Language, DDL), the user can easily in the database of data objects defined by it.
2) data manipulation functions
DBMS also provides a data manipulation language (Data Manipulation Language, DML), the user may use data DML operations, to achieve the basic operation of the database, such as a query, insert, delete and modify.
3) operation and management of the database
In establishing a database, use and maintenance of the unified management by the database management system, unified control, to ensure the security, integrity, multi-user concurrent use of the data and the system after a failure data recovery. E.g:
- Data integrity checking to ensure that data corresponding to the user input constraint conditions should be met;
- Security features of the database to ensure that only the user gives permission to access data in the database;
- Database concurrency control allows multiple users to concurrently access data from the database at the same time;
- Recovery database system so that the database can run database recovery when failures occur, to ensure reliable operation of the database.
4) provide the interface and tools easily and efficiently access a database of information
Programmers can develop database applications through the interface between programming languages and databases. Database Administrator (Database Administrator, DBA) database can be managed by tools provided.
Database administrators are specialized personnel to maintain and manage the database.
5) the establishment and maintenance of database functions
Database features include a database of initial data, conversion dump database recovery, re-organization function and performance monitoring databases, analysis functions. These functions are usually done by the use of some programs.
Database system refers to the system after the introduction of the database in a computer system. A complete database system (Database System, DBS) generally consists of a database, database management systems, application development tools, applications, database administrators and users. Full structural relationship database system as shown:
Learn SQL language
- Integration: SQL data definition set, data manipulation and data control in one, the work can be completed in the database.
- Use flexible: SQL has two ways, you can directly use the command interactively; use can also be embedded, embedded C, C ++, Fortran, COBOL, Java and other languages in use.
- Non-procedural: just to mention operating requirements, the steps need not be described, you do not need to navigate. Just tell the computer when using the "what", without the need to tell it "how to do."
- Concise language, the syntax is simple, easy to learn: In the ANSI standard, contains only 94 English words, the core functionality of only six verbs, grammar close to the spoken English.
Note: SQL statements are not case sensitive, many SQL keywords SQL developers are accustomed to conduct its own capital, and lowercase for the name of the table or column, which can improve code readability and maintainability. This tutorial is also organized in this way SQL statements. Most databases support a common SQL statements, while a different database SQL language has its own unique characteristics.
Database Access Technology
Database access technology, including ODBC, DAO, OLE DB and ADO.
ODBC
ODBC (Open Database Connectivity, Open Database Connectivity) is a Windows Open Services Architecture (Windows Open Services Architecture, WOSA) relating to a part of the database, it establishes a set of specifications, and provides a set of standards for database access API (application programming Interface). These API use SQL to accomplish most of its tasks.
ODBC itself also provides support for SQL language, users can directly SQL statements sent to ODBC.
DAO
DAO (Data Access Object, Data Access Objects set) are available from Microsoft database access technology based on a collection of objects, the database can be accessed in an independent DBMS.
OLE DB
OLE DB (Object Linking and Embedding Database , Object Linking and Embedding) is lower application programming interface Microsoft strategically leading to different data sources. OLE DB data includes not only the standard Microsoft interfaces funded, Open Database Connectivity (ODBC) Structured Query Language (SQL) capability, but also has other non-SQL data types for passage.
As Microsoft's Component Object Model (COM) a design, OLE DB is a set of read and write data method (in the past might be called channels). OLD DB includes data objects in the source object, an object stage, a command-line objects and group objects.
ADO
ADO (ActiveX Data Objects) is a COM component for accessing data sources, providing an intermediate layer programming language and unified data access OLE DB, allowing developers to write code to access the data without worrying about how the database is implemented only concerned with the connection to the database.
Access to the database when about SQL knowledge is not necessary, but a specific database support SQL commands can still be performed by the ADO Command object.