Novice Learn Oracle Common questions _oracle

Novice Oracle, there will be two big questions: First, index range Scan (scan), second, index unique scan (indexed unique scan), the following two questions through a pictorial way to give you a detailed description:

1, Index range Scan (index range scan)

Copy Code code as follows:

Select Empno,ename from emp where empno >1orderby empno

In this case, the index range scan is not used?

Second, the index unique Scan (index unique scan)

When the data type is inconsistent, the index unique scan is not performed, but the actual still unique index.

Copy Code code as follows:

Select Empno,ename from emp where empno= ' 10 '

The above is the novice to learn Oracle common questions, I hope you can enjoy.