因为是正确的区分大小写的排序规则离子排序顺序。 区分大小写排序顺序中对此进行了解释，它与 Unicode排序规范有关。 aa 将排在 AA 之前，但 AA 将排在前面的 ab 。

Because that is the correct case sensitive collation sort order. It is explained in Case Sensitive Collation Sort Order why this is the case, it has to do with the Unicode specifications for sorting. aa will sort ahead of AA but AA will sort ahead of ab.