说到连表查询，我们先了解下别名。别名可以用在表上，也可以用在表中参数名。即 SELECT "表格别名". "表中参数名" "表中参数别名" FROM “表格名” "表格别名" 或 SELECT "表格别名". "表中参数名" AS "表中参数别名" FROM “表格名” AS "表格别名" 举个例子 SELECT SI.store_name STORE, SUM(SI.sales) Total Sales FROM Story_Info SI GROUP BY SI.store_name HAVING SUM(SI.sales) > 1000;
| STORE | Total Sales |
| A | 2000 |
Store_Info表：
| store_name | sales | Date |
| A | 500 | 01-01-2000 |
| B | 200 | 02-01-2000 |
| C | 1500 | 02-10-2000 |
| D | 1000 | 03-08-2000 |
Factory表：
| factory_name | store_name |
| FA | A |
| FB | B |
| FC | C |
| FE | E |
链表查询，SQL语句中最基本的就是JOIN，可分为
INNER JOIN 两个表中，只匹配相同的列值所在行的数据。
SELECT * From Store_Info A INNER JOIN Factory B ON A.store_name = B.store_name 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| A | 500 | 01-01-2000 | FA | A |
| B | 200 | 02-01-2000 | FB | B |
| C | 1500 | 02-10-2000 | FC | C |
LEFT OUTER JOIN 返回左表的所有数据，右表中不能匹配的列值，其所在行使用空值
SELECT * FROM Store_Info A LEFT OUTER JOIN Factory B ON A.store_name = B.store_name 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| A | 500 | 01-01-2000 | FA | A |
| B | 200 | 02-01-2000 | FB | B |
| C | 1500 | 02-10-2000 | FC | C |
| D | 1000 | 03-08-2000 |
LEFT OUTER JOIN - WHERE NULL 返回和右表不匹配的所有数据行
SELECT * FROM Store_Info A LEFT OUTER JOIN Factory B ON A.store_name = B.store_name WHERE B.store_name IS NULL 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| D | 1000 | 03-08-2000 |
RIGHT OUTER JOIN 返回右表的所有数据，左表中不能匹配的列值，其所在行使用空值
SELECT * FROM Store_Info A RIGHT OUTER JOIN Factory B ON A.store_name = B.store_name 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| A | 500 | 01-01-2000 | FA | A |
| B | 200 | 02-01-2000 | FB | B |
| C | 1500 | 02-10-2000 | FC | C |
| FE | E |
RIGHT OUTER JOIN - WHERE NULL 返回和左表不匹配的所有数据行
SELECT * FROM Store_Info A RIGHT OUTER JOIN Factory B ON A.store_name = B.store_name WHERE A.store_name IS NULL 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| FE | E |
FULL OUTER JOIN 返回两个表的所有数据，如果匹配的列的值两个表都有，返回数据行，否则返回空值。
SELECT * From Store_Info A FULL OUTER JOIN Factory B ON A.store_name = B.store_name 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| A | 500 | 01-01-2000 | FA | A |
| B | 200 | 02-01-2000 | FB | B |
| C | 1500 | 02-10-2000 | FC | C |
| D | 1000 | 03-08-2000 | ||
| FE | E |
FULL OUTER JOIN -WHERE NULL 返回 INNER JOIN以外的数据行
SELECT * FROM Store_Info A FULL OUTER JOIN Factory B ON A.store_name = B.store_name WHERE A.store_name IS NULL OR B.store_name IS NULL 得出的结果：
| store_name | sales | Date | factory_name | store_name |
| D | 1000 | 03-08-2000 | ||
| FE | E |
标签：语句,01,JOIN,name,链表,2000,SQL,OUTER,store From： https://www.cnblogs.com/xiaocai84/p/17488227.html