Logical tiers may span physical tiers, and one or more or all the tiers may be allocated to one physical tier.
逻辑层可以跨物理层,并且可以将一个或多个、甚至所有的层分配到一个物理层。
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Some input is numeric or has a specified pattern In these cases, you can use the logical filtering options and check data against an expression or other logical tests.