You do not join from the parent table to the child table, or more generally the foreign key columns do not support an important access path to the child table and you do not use them in predicates to select data from this table (such as DEPT to EMP).
You do not join from the parent table to the child table, or more generally the foreign key columns do not support an important access path to the child table and you do not use them in predicates to select data from this table (such as DEPT to EMP).
大概意思是你不能通过父表向子表中插入数据，也就是说外键不支持。
比如说在dept表中只有10,20,30和40部门，那你在插入emp表的deptno列的时候不能超出这几个值。大概大概就这个意思吧。
Listen to sqysl. Read the original article with context and you'll see any guess without the context is likely to be wrong:
http://searchoracle.techtarget.c ... ign-keys-be-indexed
"So, when do you not need to index a foreign key? In general, when the following conditions are met:
...[the quoted text]..."
Yong Huang
