带“选择*"的默认SQL结果排序顺序是什么? [英] What is the default SQL result sort order with 'select *'?

问题描述

如果执行select * from mytable，将以什么顺序显示记录?它会采用第一列还是通过某种元数据对其进行排序?

If I perform a select * from mytable, in which order will the records get displayed? Will it take the first column or order it by some sort of meta data?

我正在使用Oracle数据库.

I am using an Oracle Database.

推荐答案

默认的排序"顺序为 否 .关系表中的行未排序.

There is NO default "sort" order. Rows in a relational table are not sorted.

获取特定订单的唯一方法(实际上是唯一的方法)是使用ORDER BY

The only (really: the only) way to get a specific order is to use an ORDER BY

运行不带ORDER BY的SELECT时看到的任何顺序都是完全一致的，并且可以在下次执行时更改.

Whatever order you see when running a SELECT without ORDER BY is pure coincident and can change with the next execution.

由于各种原因，订单可能会更改:

The order can change because of various reasons:

• 其他会话运行相同的语句
• 表格已更新
• 执行计划更改
• ...

这里有一个小的SQLFiddle，它向您显示顺序"如何更改: http://sqlfiddle.com/#!4/19d14/2

Here is a little SQLFiddle that shows you how the "order" can change: http://sqlfiddle.com/#!4/19d14/2

请注意，初始的订单"甚至与插入订单都不相同！

Note that the initial "order" is not even the same as the insertion order!

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