为完成此任务，您需要有一个表(或派生表)，其中包含您可以随后通过LEFT JOIN加入的日期.

In order to accomplish this, you need to have a table (or derived table) which contains the dates that you can then join from, using a LEFT JOIN.

SQL运用数学集的概念，如果您没有一组数据，则没有任何选择.

SQL operates on the concept of mathematical sets, and if you don't have a set of data, there is nothing to SELECT.

如果您需要更多详细信息，请相应地发表评论.

If you want more details, please comment accordingly.