GROUP BY语句中以逗号分隔的整数是什么完成的？ [英] What do comma-separated integers in a GROUP BY statement accomplish?

问题描述

我有这样一个查询：

I have a query like this:

SELECT col1, col2, col3, col4, col5, SUM(col6) AS total
FROM table_name
WHERE col1 < 99999
GROUP BY 1,2,3,4,5

<$ code> GROUP BY 语句在这里实际完成了吗？如果没有逗号分隔的整数，查询就无法正常工作。

What does the GROUP BY statement actually accomplish here? The query does not work properly without the comma-separated integers.

推荐答案

这相当于写作：

SELECT col1, col2, col3, col4, col5, SUM(col6) AS total
  FROM table_name
 WHERE col1 < 99999
 GROUP BY col1, col2, col3, col4, col5

/列在列表中的顺序位置表示，从1开始。

The numbers are the values/columns in the select-list expressed by ordinal position in the list, starting with 1.

这些数字用于强制;那么添加了在选择列表中使用表达式的功能。表达式可能会变得笨拙，并且并非所有DBMS都允许您使用GROUP BY子句中的选择列表中的显示标签或列别名，所以偶尔使用列号是有帮助的。

The numbers used to mandatory; then the ability to use the expressions in the select-list was added. The expressions can get unwieldy, and not all DBMS allow you to use 'display labels' or 'column aliases' from the select-list in the GROUP BY clause, so occasionally using the column numbers is helpful.

在您的示例中，最好使用名称 - 它们很简单。而且，一般来说，只要可以，就使用名称而不是数字。

In your example, it would be better to use the names - they are simple. And, in general, use names rather than numbers whenever you can.

这篇关于GROUP BY语句中以逗号分隔的整数是什么完成的？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！