How can I achieve a FULL JOIN effect in MySQL?

MySQL FULL JOIN?

In MySQL, the FULL JOIN operation is not directly supported. However, it is possible to achieve a similar result using a combination of LEFT JOIN and RIGHT JOIN. Here's how you can do it:

SELECT
    t1.column1,
    t2.column2
FROM
    table1 AS t1
LEFT JOIN
    table2 AS t2
ON
    t1.id = t2.id
UNION ALL
SELECT
    t1.column1,
    NULL
FROM
    table1 AS t1
RIGHT JOIN
    table2 AS t2
ON
    t1.id = t2.id
WHERE
    t2.id IS NULL

In this query, the LEFT JOIN retrieves all the rows from table1 and matches them with corresponding rows from table2 based on the id column. The RIGHT JOIN retrieves all the rows from table2 and matches them with corresponding rows from table1. The UNION ALL operator combines the results of both joins.

Let's say we have two tables, "Persons" and "Orders", with the following data:

Persons
P_Id	LastName	FirstName
1	Hansen	Ola
2	Pettersen	Kari
3	Svenson	Tove

Orders
OrderNo	P_Id
22456	1
24562	1
77895	2
44678	2
34764	3

To get the following result using the above query:

LastName	FirstName	OrderNo
Hansen	Ola	22456
Hansen	Ola	24562
Pettersen	Kari	77895
Pettersen	Kari	44678
Svenson	Tove	34764

Simply replace table1 with "Persons" and table2 with "Orders" in the query and execute it.

The above is the detailed content of How can I achieve a FULL JOIN effect in MySQL?. For more information, please follow other related articles on the PHP Chinese website!