Summary of new features in Oracle 12C SQL

Summary of new features in Oracle 12C SQL

Multiple indexes on the same field

Before Oracle 12c R1, a field cannot have multiple indexes in any form. Some may wonder why a field usually requires multiple indexes. In fact, there are many fields or field sets that require multiple indexes. In 12c R1, as long as the index type is different, a field can be included in a B-tree index, or in a Bitmap index. Note that only one type of index is available at a given time.

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Paging Query

In earlier versions, you need to use ROWNUM to set a "label" for the query results to implement paging query.

Introducing OFFSET and FETCH in 12c to implement quick Paging

Invisible Field

In earlier versions, to hide important data fields to avoid displaying them in common queries, we often create a view to hide the required information or apply certain security conditions.

In 12c R1, you can create invisible fields in the table. When a field is defined as invisible, this field will not appear in a common query, unless explicitly mentioned in an SQL statement or condition, or DESCRIBED is included in the table definition. It is very easy to add or modify an invisible field, and vice versa.

When fields are defined as invisible, they are not displayed when the table structure is described. However, you can make the following settings at the SQL * Plus prompt to display information about invisible fields:

SQL> SET COLINVISIBLE ON | OFF;

The preceding settings are only valid for the DESCRIBE command. Currently, it cannot produce results for SELECT statements on invisible fields.

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