对于SELECT 语句中的TABLE_references 部分,
Oracle 引擎支持下面的JOIN 语法:
table_reference[, table_reference]
table_reference [INNER | CROSS | FULL] JOIN table_reference [join_condition]
table_reference [LEFT | RIGHT [OUTER]] JOIN table_reference [join_condition]
table_reference 定义为:
[database_name.]table_name [[AS] alias]
join_condition 定义为:
ON conditional_expr | USING (column_list)