文档介绍：Module 5: 多表连接 Overview ?使用表的别名?从多个表中合并数据?合并多个结果集使用表的别名? Example 1 (without an alias name) ? Example 2 (with an alias name) USE joindb SELECT buyer_name, , qty FROM buyers AS b INNER JOIN sales AS s ON = GO USE joindb SELECT buyer_name, , qty FROM buyers AS b INNER JOIN sales AS s ON = GO USE joindb SELECT buyer_name, , qty FROM buyers INNER JOIN sales ON = GO USE joindb SELECT buyer_name, , qty FROM buyers INNER JOIN sales ON = GO?从多个表中合并数据?连接概述?使用内连接?使用外连接?使用交叉连接?连接两个以上的表?把一个表和他自身连接连接概述? Selects Specific Columns from Multiple Tables ? JOIN keyword specifies that tables are joined and how to join them ? ON keyword specifies join condition ? Queries Two or More Tables to Produce a Result Set ? Use primary and foreign keys as join conditions ? Use mon to specified tables to join tables USE joindb SELECT buyer_name, , qty FROM buyers INNER JOIN sales ON = GO USE joindb SELECT buyer_name, , qty FROM buyers INNER JOIN sales ON = GO使用内连接 sales buyer_id buyer_id buyer_id prod_id prod_id prod_id qty qty qty 1 11 14 43 3 2 23 31 15 5 15 15 5 5 37 37 11 11 4 42 2 1003 1003 buyers buyer_name buyer_name buyer_name Adam Barr Adam Barr Sean Chai Sean Chai Eva Corets Eva Corets Erin O ’ Melia Erin O ’ Melia buyer_id buyer_id buyer_id 1 12 23 34 4 Result buyer_name buyer_name buyer_name Adam Barr Adam Barr Adam Barr Adam Barr Erin O ’ Melia Erin O ’ Melia Eva Corets Eva Corets buyer_id buyer_id buyer_id qty qty qty 1 11 14 43 3 15 15 5 5 37 37 11 11 Erin O ’ Melia Erin O ’ Melia 4 4 1003 1003 Example 1 Example 1 USE joindb SELECT buyer_name, , qty FROM buyers LEFT OUTER JOIN sales ON = GO USE joindb SELECT buyer_name, , qty FROM buyers LEFT OUT