vf9新函数 ICASE( ) 函数

本文介绍了VFP9中特有的ICASE()函数,该函数功能类似于CASE WHEN...语句,适用于对同一变量进行条件赋值。文章对比了VFP与其他数据库系统中的条件表达式,并解释了ICASE()函数如何简化复杂条件下的程序编写。

在oracle和sql   server   中都有   case   when   then     else   end   或   decode   的语法,使用时非常方便
VFP中是否有类似的语法呢?

 

 

VFP9   的ICASE()函数与CASE   WHEN...功能一样,只有VFP9有,VFP8、VFP7、VFP6   没有此函数

ICASE( ) 函数
VFP9: ICASE( lCondition1, eResult1 [, lCondition2, eResult2] ...   [, eOtherwiseResult])
VFP6: 无
说明: 使用该函数,类似在“DO CASE...ENDCASE”语句对同一变量赋值。如果条件较多,组合使用IIF( )函数会使程序变得难读,使用本函数则可以较清晰。

Another example is the SRIOV_NET_VF resource class, which is provided by SRIOV-enabled network interface cards. In the case of multiple SRIOV-enabled NICs on a compute host, different qualitative traits may be tagged to each NIC. For example, the NIC called enp2s0 might have a trait “CUSTOM_PHYSNET_PUBLIC” indicating that the NIC is attached to a physical network called “public”. The NIC enp2s1 might have a trait “CUSTOM_PHYSNET_INTRANET” that indicates the NIC is attached to the physical network called “Intranet”. We need a way of representing that these NICs each provide SRIOV_NET_VF resources but those virtual functions are associated with different physical networks. In the resource providers data modeling, the entity which is associated with qualitative traits is the resource provider object. Therefore, we require a way of representing that the SRIOV-enabled NICs are themselves resource providers with inventories of SRIOV_NET_VF resources. Those resource providers are contained on a compute host which is a resource provider that has inventory records for other types of resources such as VCPU, MEMORY_MB or DISK_GB. This spec proposes that nested resource providers be created to allow for distinguishing details of complex components of some resource providers. During review the question came up about “rolling up” amounts of these nested providers to the root level. Imagine this scenario: I have a NIC with two PFs, each of which has only 1 VF available, and I get a request for 2 VFs without any traits to distinguish them. Since there is no single resource provider that can satisfy this request, it will not select this root provider, even though the root provider “owns” 2 VFs. This spec does not propose any sort of “rolling up” of inventory, but this may be something to consider in the future. If it is an idea that has support, another BP/spec can be created then to add this behavior.
07-23
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