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The basic concepts of a database:

Dynamic website development is inseparable from data storage, data storage is inseparable from database, database technology is an important part of computer technology, and plays a vital role in software development and other fields. The so-called database can be understood as a warehouse used to store information. And information is some data to be stored, such as the user's name, age, product price, profile, a certain date, time, or even an image, and so on. In short, all the data that can be stored in the computer can be stored in the database through various methods, and the database is not just a simple warehouse, it provides a series of scientific data storage, data acquisition, and other management measures.

For example, in the MySQL database we are going to learn, the information is not disorganized directly in the MySQL database, but can be vividly seen as organized in the form of a two-dimensional table, one by one stored in the table.

This is consistent with the various forms often used in daily life. Each piece of information in the table is called a record. There can be several tables in a database, and several records can be stored in each table. Each table has its own "header". For example, to design a table to count student information, then divide the student information to be collected into several columns, these columns are "table headers", in database technology, called fields. The horizontal field values in the table form a record, and multiple records form a data table. The concepts of databases, tables, fields, and field values are briefly described above. Database system is actually a software system, through which a large amount of data can be stored and managed. There are dozens of databases on the market at present. For website development, MySQL is the most widely used database in current web development, especially in PHP development.

To sum up:

Database: a warehouse for information storage, including a series of relationship measures!

Tables: there can be several tables in a database (formally you can see the tables we build in our daily life)

Fields: the information in the table is stored in several columns. These columns are called "fields" in database technology, and the specific information stored in the columns is called "field values".

Record: a piece of information we call a record several databases can be established in a database management system, and several tables can be established in each database, and there can be several records in each table.

Data types supported by MYSQL:

In order to distinguish the data of different nature and improve the efficiency of data query and operation, the database system divides the data that can be stored into many types. For example, information such as name and gender is a string type, information such as age, price and score is numeric, and date is date-time type. The data type is for fields. Some materials are called "column type" or "field type". Once a field is set to a certain type, only that type of data can be stored in that field. The data types in the MySQL database are divided into three categories: numeric type, date type, and string type.

Getting started with SQL:

Brief introduction of SQL language:

Baidu itself, this will not be described here.

SQL classification:

1.DDL (Data Definition Languages) statement

Data definition statements, through which you can create and delete changes to the database

2.DML (Data Manipulation Language) statement

Data manipulation statements for adding, deleting, updating, and querying database records and checking data integrity

3DCL (Data Control Language) statement

Data control statements, through which the relevant permissions of the database can be set

4.DDL statement

A language that creates, deletes, modifies objects within a database, and DDL statements are mostly made up of

Used by database administrators (DBA) and rarely used by developers

5.DML statement

DML operation refers to the operation of table records in the database, including inserts, updates, deletions,

And queries are the most frequently used daily operations by developers.

6.DCL statement

DCL statements are mainly used by DBA to manage object permissions in the system, and are rarely used by ordinary developers. We will explain more about the permission setting later!

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