Shulou(Shulou.com)06/01 Report--

This article is about how to use table joins in MySQL and PHP. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Table join

A table join (JOIN) is a join condition between multiple tables. Correlate tables so that data can be obtained from multiple tables.

Table join syntax:

SELECT table name 1. Column name, table name 2. Column name FROM Table 1, Table 2 WHERE condition

Several ways to join tables:

Internal connection: join or inner join

Self-join: connections in the same table

External connection:

Left outside connection, left join

Right outer connection, right join

Full external connection, full join

Data (table1)

Data (table2)

Internal connection

An inner join deletes all rows from the result table that do not match the other joined tables. (intersection)

Format:

SELECT A.c1, B.c2 FROM A JOIN B ON A.c3 = B.c3

Example:

Output result:

Database link successful

The SQL statement was executed successfully!

Array

(

[name] = > Yang Fugui

[age] = > 18

[class] = > math class

)

Array

(

[name] = > Yang Mei

[age] = > 19

[class] = > Chinese course

)

Array

(

[name] = > Yang Jianguo

[age] = > 20

[class] = > English course

)

Left connection

Contains all rows that make the table (regardless of whether there are matching rows in the right table), and all matching rows in the right table.

Format:

SELECT A.c1, B.c2 FROM A LEFT JOIN B ON A.c3 = B.c3

Example:

Output result:

Database link successful

The SQL statement was executed successfully!

Array

(

[name] = > Yang Fugui

[age] = > 18

[class] = > math class

)

Array

(

[name] = > Yang Mei

[age] = > 19

[class] = > Chinese course

)

Array

(

[name] = > Yang Jianguo

[age] = > 20

[class] = > English course

)

Array

(

[name] > Yang Tiezhu

[age] = > 21

[class] = >

)

Right connection

Contains all rows of the right table (regardless of whether there are matching rows in the left table) and all matching rows in the left table.

Format:

SELECT A.c1, B.c2 FROM A RIGHT JOIN B ON A.c3 = B.c3

Example:

Output result:

Database link successful

The SQL statement was executed successfully!

Array

(

[name] = > Yang Fugui

[age] = > 18

[class] = > math class

)

Array

(

[name] = > Yang Mei

[age] = > 19

[class] = > Chinese course

)

Array

(

[name] = > Yang Jianguo

[age] = > 20

[class] = > English course

)

Array

(

[name] = >

[age] = >

[class] = > History course

)

Full connection

Contains all rows of the left and right tables (regardless of whether there is a matching row in the other table or not).

Format:

SELECT A.c1, B.c2 FROM A LEFT JOIN B ON A.c3 = B.c3

UNION

SELECT A.c1, B.c2 FROM A RIGHT JOIN B ON A.c3 = B.c3

Example:

Output result:

Database link successful

The SQL statement was executed successfully!

Array

(

[name] = > Yang Fugui

[age] = > 18

[class] = > math class

)

Array

(

[name] = > Yang Mei

[age] = > 19

[class] = > Chinese course

)

Array

(

[name] = > Yang Jianguo

[age] = > 20

[class] = > English course

)

Array

(

[name] > Yang Tiezhu

[age] = > 21

[class] = >

)

Array

(

[name] = >

[age] = >

[class] = > History course

)

Thank you for reading! This is the end of this article on "how to use table joins in MySQL and PHP". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it out for more people to see!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.