selective table的意思|示意

If the table in your query are pretty small (usually fewer than 1,000 rows) or clustered tables, and your query is not selective at all, it would be beneficial to use a table scan.

如果查询中的表极其小(通常少于1,000行)或者是群集表，而且查询根本没有选择性的话，那么使用表扫描会更好一些。

The table is logically joined to itself, and the more selective non-leading index keys are applied as index bound filters to each unique combination of the leading key values.

首先在逻辑上将表与其自身连接，然后将更具有选择性的非起始索引键作为索引绑定过滤器，应用于起始键值的每个惟一的组合。

If this table had many columns, you would want to be selective about which columns you pick.

如果这个表有很多列，您可能希望能有选择地检取某些列。