Datatypes
Datatypes
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数据类型
DOI：
10.1007/978-1-4842-7499-6_12
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
T. Kyte
中科院分区：
文献类型：
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作者：
Darl Kuhn;T. Kyte
有很多数据库可供选择。本章将探讨22个内置数据库中的每一个，解释它们是如何实现的，以及如何以及何时使用每一个。首先是对国家语言支持（NLS）的简要概述，这是完全理解Oracle中简单字符串类型所必需的基本知识。然后我们继续讨论无处不在的数字类型。接下来，主要从历史的角度介绍LONG和LONG RAW类型。这里的主要目标是展示如何处理应用程序中的遗留LONG列并将它们迁移到LOB类型。接下来，我们将深入研究用于存储日期和时间的各种数据库，并研究如何操作各种数据库以从中获取我们需要的内容。还介绍了时区支持的来龙去脉。接下来是LOB数据库。我们将介绍它们是如何存储的，以及IN ROW、CHUNK、RETENTION、CACHE等许多设置中的每一个对我们意味着什么。在处理LOB时，了解它们是如何实现的以及默认情况下是如何存储的是很重要的，尤其是在调优它们的检索和存储时。在本章的最后，我们来看看ROWID和UROWID类型。这些是Oracle专有的特殊类型，表示行的地址。我们将介绍何时将它们用作表中的列数据类型（这几乎是不可能的）。最后，我们将介绍新的JSON数据类型并探索其用途。
There are a lot of datatypes to choose from. This chapter explores each of the 22 built-in datatypes, explaining how they are implemented, and how and when to use each one. First up is a brief overview of National Language Support (NLS), a basic knowledge of which is necessary to fully understand the simple string types in Oracle. We then move on to the ubiquitous NUMBER type. Next the LONG and LONG RAW types are covered, mostly from a historical perspective. The main objective here is to show how to deal with legacy LONG columns in applications and migrate them to the LOB type. Next, we delve into the various datatypes for storing dates and time, and investigating how to manipulate the various datatypes to get what we need from them. The ins and outs of time zone support are also covered.Next up are the LOB datatypes. We’ll cover how they are stored and what each of the many settings such as IN ROW, CHUNK, RETENTION, CACHE, and so on mean to us. When dealing with LOBs, it is important to understand how they are implemented and how they are stored by default—especially when it comes to tuning their retrieval and storage. We close the chapter by looking at the ROWID and UROWID types. These are special types, proprietary to Oracle, that represent the address of a row. We’ll cover when to use them as a column datatype in a table (which is almost never). Lastly, we cover the new JSON datatype and explore its uses.