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This article mainly explains "the difference between the inner connection, the left connection and the right connection of the database". The content in the article is simple and clear, and it is easy to learn and understand. let's study and learn the difference between the inner connection, the left connection and the right connection of the database.

Here to share the various connections to the database.

First create a database with navicat

Create table A, BBJ SQL in the same way

CREATE TABLE `A` (

`Aid` int (10) NOT NULL DEFAULT 1 COMMENT 'Primary key'

`Aname` varchar2

PRIMARY KEY (`id`)

)

ENGINE=InnoDB

DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci

ROW_FORMAT=DEFAULT

The record with select* from An is shown in figure 1 below:

The record with select* from B is shown in figure 2 below:

The relationship between An and B is shown in the figure:

Internal connection (Inner JOIN):

Select* from A JOIN B ON A.Aid=B.Bnameid

Or: select* from A Magi B where A.Aid=B.Bnameid

Running effect

Left connection (Left JOIN):

Select* from A Left JOIN B ON A.Aid=B.Bnameid

Running effect

Right connection (Right JOIN):

Select* from A Right JOIN B ON A.Aid=B.Bnameid

Running effect

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