Question

我已阅读并重试以下方面重建以下内容，但为了清楚说明，我将展示我的最后一次尝试。

目标 - 获取列“UniqueID”的最大值

列字段'uniqueID'设置为bigint

我认为错误与addwithvalue一致，因为我得到“int”作为返回值

如果我运行查询SELECT MAX(UniqueID) FROM tblResults in SQL，则可以正常运行

代码

 Dim connection5 As SqlConnection
    Dim command5 As New SqlCommand
    Dim ds5 As New DataSet
    Dim ConnectionString5 As String = System.Configuration.ConfigurationManager.ConnectionStrings("mySQLConnectionString").ToString()
    connection5 = New SqlConnection(ConnectionString5)

    connection5.Open()
    command5.Connection = connection5
    command5.Parameters.Clear()

    command5.CommandText = "spUniqueUserID"
    command5.Parameters.AddWithValue("@UniqueID", SqlDbType.BigInt)
    command5.Parameters("@UniqueID").Direction = ParameterDirection.Output
    command5.CommandType = CommandType.StoredProcedure
    command5.ExecuteNonQuery()

    Session.Item("UniqueID") = command5.Parameters("@UniqueID").Value
    connection5.Close()

    Dim vShow As String
    vShow = ""
    vShow = Session.Item("UniqueID").ToString

SP

USE [DB]
GO
/****** Object:  StoredProcedure [dbo].[spUniqueUserID]    Script Date: 09/10/2013 08:51:57 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [dbo].[spUniqueUserID]

@UniqueID bigint OUTPUT

AS

BEGIN

select @UniqueID = (SELECT MAX(UniqueID) FROM tblResults )

Return @UniqueID

END

Answer 1

我个人不会搞砸输出参数。只需使用

ALTER PROCEDURE [dbo].[spUniqueUserID]

AS

BEGIN

 SELECT MAX(UniqueID) FROM tblResults

END

你的过程中的

和

Dim sqlConnection1 As New SqlConnection("Your Connection String")
Dim cmd As New SqlCommand
Dim returnValue As Object

cmd.CommandText = "spUniqueUserID"
cmd.CommandType = CommandType.StoredProcedure
cmd.Connection = sqlConnection1

sqlConnection1.Open()

returnValue = cmd.ExecuteScalar()

sqlConnection1.Close()

在你的代码中。（最好使用连接和命令的语句，为简洁起见，此处缺失）

Answer 2

尝试

 command5.Parameters.AddWithValue("@UniqueID", 0L)

AddWithValue确定要传递给底层引擎的参数的DataType，以查看第二个参数的数据类型。你传递一个字符串，这当然是错的。

在替代方案中，您可以明确定义参数

 Dim parameter = new SqlParameter("@UniqueID", SqlDbType.BigInt)
 parameter.Direction = ParameterDirection.Output
 parameter.Size = 8
 parameter.Value = 0
 command5.Parameters.Add(parameter)

并且，作为最后但基本步骤，不要忘记指定此命令执行storedprocedure然后执行命令

 command5.CommandType = CommandType.StoredProcedure
 command5.ExecuteNonQuery()

作为替代，但这需要更改您的存储过程，是使用ExecuteScalar。当您需要代码中的单个结果时，应使用此方法。

ALTER PROCEDURE [dbo].[spUniqueUserID]
AS

BEGIN
    select SELECT MAX(UniqueID) FROM tblResults
END

并在您的代码中

    Using connection5 = New SqlConnection(ConnectionString5)
    Using command5 As New SqlCommand("spUniqueUserID", connection5)
         connection5.Open()
         command5.CommandType = CommandType.StoredProcedure
         Dim result = command5.ExecuteScalar()
         .....
    End Using
    End Using

但是在这一点上，storedprocedure的实用性非常小，您可以直接在SqlCommand的构造函数中编写sql并删除CommandType设置

    Using connection5 = New SqlConnection(ConnectionString5)
    Using command5 As New SqlCommand("SELECT MAX(UniqueID) FROM tblResults", connection5)
         connection5.Open()
         Dim result = command5.ExecuteScalar()
         .....
    End Using
    End Using

Answer 3

 Dim ConnectionString5 As String = System.Configuration.ConfigurationManager.ConnectionStrings("mySQLConnectionString").ToString()

        Using connection5 = New SqlConnection(ConnectionString5)
            Using command5 As New SqlCommand("SELECT MAX(UniqueID) FROM tblResults", connection5)

                connection5.Open()
                Dim result = command5.ExecuteScalar()

                Session.Item("UniqueID") = result
                connection5.Close()
            End Using
        End Using

        Dim vShow As String
        vShow = ""
        vShow = Session.Item("UniqueID").ToString

使用存储过程返回Max

3 个答案: