什么是 Oracle 隐藏字段? [英] What are Oracle hidden fields?

问题描述

ALL_TAB_COLS 不同于 ALL_TAB_COLUMNS 隐藏的列没有被过滤掉.

ALL_TAB_COLS differs from ALL_TAB_COLUMNS in that hidden columns are not filtered out.

什么是隐藏字段?

此视图与ALL_TAB_COLUMNS"的不同之处在于隐藏的列是没有过滤掉.

This view differs from "ALL_TAB_COLUMNS" in that hidden columns are not filtered out.

推荐答案

隐藏列是表中存在但无法选择的列.Oracle 可能会创建隐藏列的原因有多种 - 两个更常见的原因是

Hidden columns are columns that exist in the table but that cannot be selected. There are various reasons that Oracle might create a hidden column-- two of the more common reasons are

• 当一列被标记为未使用但未被删除时，它被隐藏
• Oracle 虚拟列在表中创建隐藏列

• When a column is marked as unused but not dropped, it is hidden
• Oracle virtual columns create hidden columns in the table

其他各种 Oracle 功能也可能创建隐藏列，但这些功能往往更深奥(即，如果没记错的话，interMedia 会创建几个隐藏列来跟踪各种数据位).

Various other Oracle features may create hidden columns as well though those features tend to be more esoteric (i.e. if memory serves, interMedia creates a couple of hidden columns to track various bits of data).

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