CLR Table-Valued函数

时间:2023-03-08 15:35:46
CLR Table-Valued函数

这几天来,努力学习了CLR的存储过程,创建与部署。从普通的存储过程,带参数,以及Output返回值等。

Insus.NET今天学习一个例子,怎样实现CLR Table-Valued函数。在数据库中,我们可以看到很多种函数类型,Table-falued function,Scalar-valued function 等等。
CLR Table-Valued函数

这篇练习的CLR中编写的函数就是table-valued function。

在VS开发SQL的 CLR程序,有简单有复杂,看开发时的衡量了。有些在SQL中无法实现的,可以写成CLR,然后再部署至SQL中。此篇并没有看出两者之间的优势,仅是一个例子作为参考。

比如我们想创建一个多表查询LEFT JOIN。把SQL语句写成一个table-valued函数。这个多表查询,所返回的字段,定义成一个类别:
CLR Table-Valued函数

上面代码示例,可复制代码:

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlTypes;
using System.Text; namespace Insus.NET
{
class Fruit
{
public byte Fruit_nbr { get; set; }
public byte FruitCategory_nbr { get; set; }
public string CategoryName { get; set; }
public byte FruitKind_nbr { get; set; }
public string KindName { get; set; }
public string FruitName { get; set; }
}
}

创建一个新Item:
CLR Table-Valued函数

按下面的步骤,在标记5中选择SQL CLR C# User Defined Function。 CLR Table-Valued函数

标记6,给一个名字,标记7"Add"之后:
CLR Table-Valued函数

删除#14至#19行代码,添加下面代码:
CLR Table-Valued函数

上面代码示例,可复杂代码:

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Collections;
using Insus.NET;
using System.Collections.Generic; public partial class UserDefinedFunctions
{
[SqlFunction(DataAccess = DataAccessKind.Read,
FillRowMethodName = "Item_FillRow",
TableDefinition = "Fruit_nbr TINYINT,FruitCategory_nbr TINYINT, " +
"CategoryName NVARCHAR(30),FruitKind_nbr TINYINT," +
"KindName NVARCHAR(30),FruitName NVARCHAR(30)"
)
]
public static IEnumerable Tvf_Fruit()
{
List<Fruit> fruitConnections = new List<Fruit>();
using (SqlConnection connection = new SqlConnection("context connection=true"))
{
connection.Open();
string sql = "SELECT [Fruit_nbr],[FruitCategory_nbr],[CategoryName]," +
"u_fk.[FruitKind_nbr],[KindName],[FruitName] FROM [dbo].[Fruit] AS f " +
"LEFT JOIN [dbo].[udf_FruitKind]() AS u_fk ON (f.[FruitKind_nbr] = u_fk.[FruitKind_nbr])";
using (SqlCommand command = new SqlCommand(sql, connection))
{
using (SqlDataReader objDr = command.ExecuteReader())
{
while (objDr.Read())
{
Fruit oFruit = new Insus.NET.Fruit();
oFruit.Fruit_nbr = (byte)objDr["Fruit_nbr"];
oFruit.FruitCategory_nbr = (byte)objDr["FruitCategory_nbr"];
oFruit.CategoryName = objDr["CategoryName"].ToString();
oFruit.FruitKind_nbr = (byte)objDr["FruitKind_nbr"];
oFruit.KindName = objDr["KindName"].ToString();
oFruit.FruitName = objDr["FruitName"].ToString();
fruitConnections.Add(oFruit);
}
}
}
}
return fruitConnections;
} private static void Item_FillRow(object source, out SqlByte fruit_nbr,
out SqlByte fruitCategory_nbr, out SqlChars categoryName,
out SqlByte fruitKind_nbr, out SqlChars kindName, out SqlChars fruitName)
{
Fruit fruit = (Fruit)source;
fruit_nbr = new SqlByte(fruit.Fruit_nbr);
fruitCategory_nbr = new SqlByte(fruit.FruitCategory_nbr);
categoryName = new SqlChars(fruit.CategoryName);
fruitKind_nbr = new SqlByte(fruit.FruitKind_nbr);
kindName = new SqlChars(fruit.KindName);
fruitName = new SqlChars(fruit.FruitName);
}
}

接下来,Build,然后可以部署至SQL中去。
CLR Table-Valued函数

上面可复制代码:

IF EXISTS (SELECT * FROM sys.objects WHERE name = 'Tvf_Fruit')
DROP FUNCTION Tvf_Fruit;
GO IF EXISTS (SELECT * FROM sys.assemblies WHERE name = 'FruitClr')
DROP ASSEMBLY FruitClr;
GO CREATE ASSEMBLY FruitClr
FROM 'E:\FruitClr.dll'
WITH PERMISSION_SET = SAFE;
GO CREATE FUNCTION Tvf_Fruit()
RETURNS TABLE (
Fruit_nbr TINYINT,
FruitCategory_nbr TINYINT,
CategoryName NVARCHAR(30),
FruitKind_nbr TINYINT,
KindName NVARCHAR(30),
FruitName NVARCHAR(30)
)
AS
EXTERNAL NAME [FruitClr].UserDefinedFunctions.Tvf_Fruit;
GO

执行成功之后,你肯定会发现SQL发生变化的两个位置:
CLR Table-Valued函数

此时table-valued function创建成功了,在查询分析器执行一下Tvf_Fruit()函数。
CLR Table-Valued函数

下面内容于2015-03-31 09:30分添加:
看看执行的效率如何? 标记1是原始写法,标记2是写成Clr函数。它们得到结果是一样的。
CLR Table-Valued函数