有件东西我观察了很多年，那就是很少有开发者会去使用SQL Server中的一个非常有用的东西——EXISTS结构。你可以在各种情况中用到EXISTS结构，在这篇文章中我会向大家介绍其中的一些。 EXISTS结构 EXISTS结构是一个TSQL函数，这个函数会就圆括号中的子查询返回一个 ...

This should be a quickie.<BR><BR>I need to write a query that has to run in a tight loop in my application, so I want to make it efficient.<BR><BR>Is there any significant difference in efficiency ...

The EXISTS condition is an operator whose right operand is a subquery. The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is ...