What is the main purpose of SQL?

Feature introduction SQL

Execute queries against the database; sql

Data can be retrieved from the database; sql

New records can be inserted into the database; sql

Updates to data in the database; sql

Records can be deleted from the database; sql

You can create a new database; sql

You can create a new table in the database; sql

Stored procedures can be created in the database; sql

Views can be created in the database; sql

You can set permissions for tables, stored procedures, and views.

Limitations of SQL. sql

It's one. ansi

A standard computer language used to access and operate database systems. SQL statements are used to retrieve and update data in the database. sql

Works with database programs, such as:

MSaccess, DB2, Informix, MSSQLServ, Oracle, Sybase, and other database systems.

Unfortunately, there are many different versions of it.

sql language, but in order to work with.

select, update, delete, insert, where, etc.). Note: Except.

Outside of the SQL standard, most of them.

SQL database programs all have their own private extensions!

1. The role of SQL:

1. SQL is mainly used for the query, summary, writing, deletion and other aspects of database series software, and is specifically used for database programming or database data maintenance.

2. In other words, SQL is generally used for database programming and troubleshooting of existing databases. Therefore, generally the programmers involved in the database or the maintenance personnel of the computer information system need to learn the knowledge of SQL (that is, the database).

1. SQL is a structured query language.

Structured Query Language).

2. At present, it is most mainly used in Microsoft.

SQL Server and Oracle Database.

Manipulation of data in the server. It is also often used as an interface instruction statement for other small databases and stand-alone databases, such as mysql and access.

3. In large-scale database applications, the SQL statements corresponding to specific functions are generally embedded into the program by program development designers, and when multiple complex SQL statements are required, they will also be written in the database server in the form of storage procedures and other methods for calling. Users often don't need to deal with specialized SQL statements.

Here's what it does:

1. The system table stores all the system information of the SQL system.

The so-called metadata stored about the metadata in the database service is (such as what user databases are available in the data server, what login accounts are available in the database server, what tables are in the database, what fields are in each table, and what stored procedures, views, and so on are stored in each database).

2. Understand the system tables in the database, which can be used when writing SQL statements or programming.

When creating a database, select whether the database exists; If an object (such as a table, view, stored procedure, or index) exists in the database, it is returned, or if it does not, the creation statement is executed. Delete objects in a database in batches, such as tables, views, and indexes created by all users in a specific database.

Third, several important system tables.

sysxlogins: Stored in the master database, (all users and roles in the database), recording all accounts that can be logged in to SQL Server. To restart the service or reconfigure with override, sysdatabases:

It records all the databases of the current system. This system table is available only in the master data.

To put it simply.

For example, the money in your bank card is stored in the database, and your usage records, whereabouts, etc. are stored in the database.

For example, now you can know your physical ID number, name, etc., which are stored in the database.

Storing and retrieving data, just like your house at home, you can put anything in your house, and then whatever you want can be taken out of your house and used.

SQL Server Database Fundamentals Lecture 1: Database 1: What is a Database? 2. What are the main functions of the database? 3. What are the commonly used database management software?

Introduction to SQL.

SQL is the standard old computer language used to access and process databases.

What is SQL?

SQL refers to Structured Query Language.

SQL lets you access and work with databases.

SQL is a computer language based on ANSI (American National Standards Institute).

What can SQL do?

SQL executes queries against the database.

SQL retrieves data from the database.

SQL can insert new records into the database.

SQL updates the data in the database.

SQL can delete the record from the database.

SQL creates a new database.

SQL can create a new table in the database.

SQL can create stored procedures in the database.

SQL creates views in a database.

SQL can set permissions for tables, stored procedures, and views.

SQL is a standard - but there are many different versions of the SQL language.

Although SQL is an ANSI (American National Standards Institute) standard computer language, there are many different versions of the SQL language.

However, in order to be compatible with the ANSI standard, they must work together in a similar way to support some of the major commands (e.g. select, update, delete, insert, where, etc.).

Note: With the exception of the SQL Standard, most SQL database programs have their own proprietary extensions!

Use SQL in your **

RDBMS database programs (e.g., MS Access, SQL Server, MySQL).

Use a server-side scripting language, such as PHP or ASP

Use SQL to get the data you want.

Use HTML CSS

RDBMSRDBMS refers to relational database management system.

RDBMS is the foundation of SQL and the roll-up foundation of all modern database systems, such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.

The data in an RDBMS is stored in database objects called tables.

A table is a collection of related data items, and it consists of columns and rows.

SQL (Structured Query Language) is used to access data and query, update, and manage relational database systems.

SQL is based on relational algebra and tuple relational calculus, including a data definition language and a data manipulation language. The scope of SQL includes data insertion, querying, updating, and deletion, database schema creation and modification, and data access control. Although it is very much declarative programming (4GL), it also contains elements of procedural programming.

SQL was the first commercial language implementation of Edgar Cod's relational model, which was described in his influential 1970 article, "A Relational Model for Large Shared Databases."

Although SQL is not fully designed according to the Referential Model of Codd, it is still the most widely used database language. SQL became a standard of the American National Standards Institute (ANSI) in 1986 and an International Organization for Standardization (ISO) standard in 1987. Since then, the standard has undergone a series of updates to include a number of new features.