sql常用语法命令及函数

For this guide we’ll discuss the SQL RIGHT JOIN.

对于本指南，我们将讨论SQL RIGHT JOIN。

正确加入 (Right Join)

The RIGHT JOIN keyword returns all records from the right table (table2), and the matched records from the left table(table1) . The result is NULL from the left side, when there is no match.

RIGHT JOIN关键字从右表(table2)返回所有记录，并从左表(table1)返回匹配的记录。 如果没有匹配项，则结果从左侧开始为NULL。

SELECT *
FROM table1
RIGHT JOIN table2
ON table1.column_name = table2.column_name;

完整的表格清单供参考 (Complete table listings for reference)

food or LEFT table data

食物或左表数据

+---------+--------------+-----------+------------+
| ITEM_ID | ITEM_NAME    | ITEM_UNIT | COMPANY_ID |
+---------+--------------+-----------+------------+
| 1       | Chex Mix     | Pcs       | 16         |
| 6       | Cheez-It     | Pcs       | 15         |
| 2       | BN Biscuit   | Pcs       | 15         |
| 3       | Mighty Munch | Pcs       | 17         |
| 4       | Pot Rice     | Pcs       | 15         |
| 5       | Jaffa Cakes  | Pcs       | 18         |
| 7       | Salt n Shake | Pcs       |            |
+---------+--------------+-----------+------------+company or RIGHT table data
``` text
+------------+---------------+--------------+
| COMPANY_ID | COMPANY_NAME  | COMPANY_CITY |
+------------+---------------+--------------+
| 18         | Order All     | Boston       |
| 15         | Jack Hill Ltd | London       |
| 16         | Akas Foods    | Delhi        |
| 17         | Foodies.      | London       |
| 19         | sip-n-Bite.   | New York     |
+------------+---------------+--------------+

To get company name from company table and company ID, item name columns from foods table, the following SQL statement can be used:

要从公司表获取公司名称和公司ID，从食品表获取项目名称列，可以使用以下SQL语句：

SELECT company.company_id,company.company_name,
company.company_city,foods.company_id,foods.item_name
FROM   company
RIGHT JOIN foods
ON company.company_id = foods.company_id;

OUTPUT

输出值

COMPANY_ID COMPANY_NAME              COMPANY_CITY              COMPANY_ID ITEM_NAME
---------- ------------------------- ------------------------- ---------- --------------
18         Order All                 Boston                    18         Jaffa Cakes
15         Jack Hill Ltd             London                    15         Pot Rice
15         Jack Hill Ltd             London                    15         BN Biscuit
15         Jack Hill Ltd             London                    15         Cheez-It
16         Akas Foods                Delhi                     16         Chex Mix
17         Foodies.                  London                    17         Mighty Munch
NULL       NULL                      NULL                      NULL       Salt n Shake

翻译自: https://www.freecodecamp.org/news/sql-right-join-command-example-syntax/

sql常用语法命令及函数