mysql LEFT JOIN多表联结查询

具体操作

MySQL支持Select和某些Update和Delete情况下的Join语法，具体语法上的细节有：
 table_references:
    table_reference [, table_reference] …
 table_reference:
    table_factor
  | join_table
 table_factor:
    tbl_name [[AS] alias]
        [{USE|IGNORE|FORCE} INDEX (key_list)]
  | ( table_references )
  | { OJ table_reference LEFT OUTER JOIN table_reference
        ON conditional_expr }
 join_table:
    table_reference [INNER | CROSS] JOIN table_factor [join_condition]
  | table_reference STRAIGHT_JOIN table_factor
  | table_reference STRAIGHT_JOIN table_factor ON condition
  | table_reference LEFT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [LEFT [OUTER]] JOIN table_factor
  | table_reference RIGHT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [RIGHT [OUTER]] JOIN table_factor
 join_condition:
    ON conditional_expr | USING (column_list)

除了常用的两个表连接之外，SQL（MySQL） JOIN 语法还支持多表连接。多表连接基本语法如下：

... FROM table1 INNER|LEFT|RIGHT JOIN table2 ON condition INNER|LEFT|RIGHT JOIN table3 ON condition ...

JOIN 多表连接实现了从多个表中获取相关数据，下面是三个原始数据表：