SQL select 语句中 Order By 1 的目的是什么?

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问题描述

我正在阅读一些工作中的旧代码，并注意到有几个带有 order by 1 子句的视图.这有什么作用?

I'm reading through some old code at work, and have noticed that there are several views with an order by 1 clause. What does this accomplish?

示例:

Create view v_payment_summary AS
SELECT A.PAYMENT_DATE,
       (SELECT SUM(paymentamount)
          FROM payment B
         WHERE PAYMENT_DATE = B.PAYMENT_DATE
           and SOME CONDITION) AS SUM_X,
       (SELECT SUM(paymentamount)
          FROM payment B
         WHERE PAYMENT_DATE = B.PAYMENT_DATE
           and SOME OTHER CONDITION) AS SUM_Y
FROM payment A
ORDER BY 1;

推荐答案

这个:

ORDER BY 1

...被称为序数"——数字代表基于 SELECT 子句中定义的列数的列.在您提供的查询中，这意味着:

...is known as an "Ordinal" - the number stands for the column based on the number of columns defined in the SELECT clause. In the query you provided, it means:

ORDER BY A.PAYMENT_DATE

这不是推荐的做法，因为:

It's not a recommended practice, because:

这并不明显/明确
如果列顺序发生变化，查询仍然有效，因此您可能会按您不希望的顺序进行排序

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