Question

首先我必须从查询表中找到代理商名称，如果代理商名称找到，那么如果没有找到代理商名称，那么部分将会发生，第二个查询数据是其他部分将起作用。下面是我的查询PLZ让我知道我错在哪里。提前致谢

create proc ConfirmationMail_ToAgent
(
    @Enquiry_Id nvarchar(50)
)
as
begin
    select Agent_Name from Enquiry where Enquiry_Id = @Enquiry_Id as jh
    if(jh != 'Select')
    begin
        select e.Agent_Name,e.Agent_Email,e.Client_Name,e.Handled_By,ef.EMail_Id from Enquiry e inner join Employee_FullDetail ef on e.Handled_By = ef.First_Name where e.Enquiry_Id = @Enquiry_Id
    end
    else
    begin
       select e.Client_Name,e.Client_Address,e.Handled_By,ef.EMail_Id from Enquiry e inner join Employee_FullDetail ef on e.Handled_By = ef.First_Name where e.Enquiry_Id = @Enquiry_Id
    end
end

Answer 1

在SQL Server中，使用以下语法

将列分配到变量中

DECLARE @Var varchar(xx)
SELECT @Var = [ColName] FROM [TableName]

所以你的查询应该是这样的：

create proc ConfirmationMail_ToAgent
(
@Enquiry_Id nvarchar(50)
)
as
BEGIN
    DECLARE @jh VARCHAR(100)
    select @jh= Agent_Name from Enquiry where Enquiry_Id = @Enquiry_Id 
    if(@jh != 'Select')
    begin
        select e.Agent_Name,e.Agent_Email,e.Client_Name,e.Handled_By,ef.EMail_Id from Enquiry e inner join Employee_FullDetail ef on e.Handled_By = ef.First_Name where e.Enquiry_Id = @Enquiry_Id
    end
    else
    begin
        select e.Client_Name,e.Client_Address,e.Handled_By,ef.EMail_Id from Enquiry e inner join Employee_FullDetail ef on e.Handled_By = ef.First_Name where e.Enquiry_Id = @Enquiry_Id
    end
end

Answer 2

我真的认为你必须阅读DRY principle in programming。请遵循此原则，它将帮助您将来维护您的代码。它看起来你不需要2个查询，你可以只使用一个：

create proc ConfirmationMail_ToAgent
(
     @Enquiry_Id nvarchar(50)
)
as
begin
    select
        case when e.Agent_Name != 'Select' then e.Agent_Name else e.Client_Name end as Name,
        case when e.Agent_Name != 'Select' then e.Agent_Email else e.Client_Address end as Address,
        e.Handled_By, ef.EMail_Id
    from Enquiry as e
        inner join Employee_FullDetail as ef on ef.First_Name = e.Handled_By
    where e.Enquiry_Id = @Enquiry_Id
end

这个更易于维护 - 如果您必须向结果集添加列，则只需执行一次，更易于阅读 - 您不必想想 - 这两个查询有什么区别？要完全遵循DRY原则，可以重写此查询，例如，如下所示：

create proc ConfirmationMail_ToAgent
(
     @Enquiry_Id nvarchar(50)
)
as
begin
    select
        C.Name, C.Email,
        e.Client_Name, e.Handled_By, ef.EMail_Id
    from Enquiry as e
        inner join Employee_FullDetail as ef on ef.First_Name = e.Handled_By
        outer apply ( 
            select e.Agent_Name, e.Agent_Email where e.Agent_Name != 'Select' union all
            select e.Client_Name, e.Client_Address where e.Agent_Name == 'Select'
        ) as C(Name, Email)
    where e.Enquiry_Id = @Enquiry_Id
end

我们可以使用一个选择查询的结果作为条件来查找记录

2 个答案: