注意行和列的次序与元素在每个集合中的顺序是相同的，索引变量名在第12、13和14行是一致的。

Note that the row and column order is the same as the element order in each set, and the index variable names are consistent between lines 12, 13, and 14.

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对于单一分组集或多个分组集，分组列的次序是无所谓的；但是对于ROLLUP，列的次序不能随意安排。

While the ordering of the grouping columns does not matter for a single grouping set or multiple grouping sets, the order of the columns does matter for ROLLUP.

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再次点击列即可切换排序的次序。

Clicking on the column again will flip the sorting order.

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