Linq To Sql进阶系列(四)User Define Function篇
[1] Linq To Sql进阶系列(四)User Define Function篇
[2] Linq To Sql进阶系列(四)User Define Function篇
[3] Linq To Sql进阶系列(四)User Define Function篇
[4] Linq To Sql进阶系列(四)User Define Function篇
[2] Linq To Sql进阶系列(四)User Define Function篇
[3] Linq To Sql进阶系列(四)User Define Function篇
[4] Linq To Sql进阶系列(四)User Define Function篇
系列文章导航:
Linq To Sql进阶系列(四)User Define Function篇
Linq To Sql进阶系列(五)Store Procedure篇
Linq To Sql进阶系列(六)用object的动态查询与保存log篇
Linq To Sql进阶系列(七)动态查询续及CLR与SQL在某些细节上的差别
4 TVF
返回一个table 的UDF称为TVF.看下面例子
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
TVF在sql中支持from,join,union等操作。同样,这些操作在Linq To Sql中一样支持。该TVF的dbml为:
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
IsComposable="true">
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
CanBeNull="false" />
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
CanBeNull="true" />
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
CanBeNull="false" />
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
ElementType子项说明了其返回一个table.映射为类的名称为ProductsUnderThisUnitPriceResult。其映射的code中,不光是一个函数,还有一个对应的返回类。当然,这个返回类的定义,可以由用户自己指定。此处不讲。我们使用默认的类。我们先来看一个from的例子
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
你可以就把该udf当作一个普通的表来使用。再举一个join操作Linq To Sql的例子
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
p.CategoryID into prods
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
因为,sql中支持TVF的in-line操作,所以Linq To Sql完全支持其对等的操作。他们所生成的sql语句不再列出。
总结:
通过本文,我们可以看出Linq To Sql完全融入了Sql中UDF,包括对其内联操作的支持。对于某些特殊需求,用户可以手工将函数映射为code,但这并不说明,任何函数都适用。