【Oracle】SQL/92 执行多个表的连接

• 内连接
• 外连接
• 自连接
• 交叉连接

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1.内连接

表名 INNER JOIN 表名 ON 条件

等价于：

FROM 表名, 表名

WHERE 条件

SELECT p.name, pt.name, pt.product_type_id

FROM products p INNER JOIN product_types pt ON p.product_type_id = pt.product_type_id

ORDER BY p.name;

表名 INNER JOIN 表名 USING (属性)

注意：在SELECT中的属性不能加前缀，如pt.product_type_id会报错

SELECT p.name, pt.name, product_type_id

FROM products p INNER JOIN product_types pt USING (product_type_id)

ORDER BY p.name;

多于两个表的内连接

SELECT c.first_name, c.last_name, p.name AS PRODUCT, pt.name AS TYPE

FROM customers c, products p, product_types pt, purchases pr

WHERE c.customer_id = pr.customer_id

AND pr.product_id = p.product_id

AND p.product_type_id = pt.product_type_id

ORDER BY p.name;

用INNER JOIN USING重写

SELECT c.first_name, c.last_name, p.name AS PRODUCT, pt.name AS TYPE

FROM customers c INNER JOIN purchases pr

USING (customer_id)

INNER JOIN products p

USING (product_id)

INNER JOIN product_types pt

USING (product_type_id)

ORDER BY p.name;

2. 外连接

SQL/92执行外连接

语法：FROM table1 {LEFT | RIGHT | full} OUTER JOIN table2

left、right分别表左、右连接

full表全连接，这是+操作符无法做到的

SELECT p.name, pt.name

FROM products p, product_types pt

WHERE p.product_type_id = pt.product_type_id (+)

ORDER BY p.name;

上面的左连接改成SQL/92形式则为：

SELECT p.name, pt.name

FROM products p LEFT OUTER JOIN product_types pt USING (product_type_id)

ORDER BY p.name;

SELECT p.name, pt.name

FROM products p, product_types pt

WHERE p.product_type_id = pt.product_type_id (+)

ORDER BY p.name;

上面的右连接改成SQL/92形式则为：

SELECT p.name, pt.name

FROM products p RIGHT OUTER JOIN product_types pt USING (product_type_id)

ORDER BY p.name;

3.自连接

使用SQL/92执行自连接

与内连接一样，只是table1与table2是同一表。

4.交叉连接

使用SQL/92进行交叉连接：

语法:FROM talbe1 CROSS JOIN table2

SELECT *

FROM products, product_types;

可以改成：

SELECT *

FROM products CROSS JOIN product_types;

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转载：

原文地址：

http://www.cnblogs.com/visayafan/archive/2011/10/20/2219612.html