为变量赋值的 SELECT 语句不得与数据检索操作结合使用 [英] A SELECT statement that assigns a value to a variable must not be combined with data-retrieval operations

问题描述

这个说法有什么问题?

ALTER Function [InvestmentReturn].[getSecurityMinLowForPeriod](@securityid int,
    @start datetime,
    @end datetime)
returns xml
begin

declare @results varchar(500)
declare @low int
declare @adjustedLow int
declare @day varchar(10)

if @end is null
begin
    set @end = getdate()
end
set @adjustedLow = (select min(adjLow) 
                        from (
                            select Low * [InvestmentReturn].[fn_getCorporateActionSplitFactor](isq.securityid, @start, convert(varchar,day, 111)) as adjLow 
                            from 
                                securityquote isq
                            where isq.securityid = @securityid and isq.day >= convert(varchar(10), @start, 111) and convert(varchar(10), @end, 111) >= isq.day
                            and low != -1 
                            ) as x)
select 
    top 1 @low = low
    , @day = day
    , @adjustedLow
--select high
from 
    securityquote sq
where 
    day >= convert(varchar(10), @start, 111) and convert(varchar(10), @end, 111) >= day
    and securityid = @securityid and low != -1
order by low asc

    set @results=  '<results type="debug_min">'
    set @results = @results + '<periodStart>' + coalesce(cast(@start as varchar(20)), 'NULL') + '</periodStart>' 
    set @results = @results + '<periodEnd>' + coalesce(cast(@end  as varchar(20)), 'NULL') + '</periodEnd>' 
    set @results = @results + '<securityID>' + coalesce(cast(@securityID as varchar(10)), 'NULL') + '</securityID>'
    set @results = @results + '<periodMin>' + coalesce(cast(@low as varchar(10)), '-11111') + '</periodMin>'
    set @results = @results + '<coraxAdjustedPeriodMin>' + coalesce(cast(@adjustedLow as varchar(10)), '-11111') + '</coraxAdjustedPeriodMin>'
    set @results = @results + '<dayMinOcurred>' + coalesce(@day, 'NULL') + '</dayMinOcurred>'
    set @results = @results + '</results>'

return @results

只是为了解释答案(在了解导致错误的位置之后)，我只是从第二个 select 语句中删除了 @adjustedLow.

Just to explain the answer (after getting where the error was caused), I simply removed @adjustedLow from the second select statement.

推荐答案

来自 SELECT 语句的列值被分配到 @low 和 @day 局部变量；@adjustedLow 值未分配给任何变量并导致问题:

Column values from the SELECT statement are assigned into @low and @day local variables; the @adjustedLow value is not assigned into any variable and it causes the problem:

问题出在这里:

select 
    top 1 @low = low
    , @day = day
    , @adjustedLow  -- causes error!
--select high
from 
    securityquote sq
...

详细说明和解决方法:SQL Server 错误消息 - Msg 141- 为变量赋值的 SELECT 语句不得与数据检索操作结合使用.

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