SQL Server 2008 R2 在强制转换 varchar->time 时失败

Question

我在我们的 SQL Server 2008 R2 服务器中遇到了一个奇怪的错误。 varchar 到 time 的转换失败，具体取决于顶级语句的 SELECT 子句中使用的其他列。重现问题的代码

CREATE FUNCTION [dbo].[explode]
(
    @haystack varchar(max),
    @separator varchar(8000)
)
RETURNS 
@ret TABLE 
(
    orderCol int identity(1,1),
    value varchar(max)
)
AS
BEGIN
    declare @index bigint
    set @index = charindex(@separator,@haystack)
    while @index > 0
    begin
        insert into @ret (value) values (substring(@haystack,1,@index-1))
        set @haystack = substring(@haystack,@index+len(@separator),len(@haystack)-@index-len(@separator)+1)
        set @index = charindex(@separator,@haystack)
    end
    insert into @ret (value) select @haystack
    RETURN 
END

还有查询：

declare @s varchar(1000) = 'a,2015-10-08,1451,1,2,3,4,5,6,7,8,9,10,11;a,2015-10-08,1721,12,13,14,15,16,17,18,19,20,21,22'
declare @units varchar(1000) = 'l1,l2,l3,l4,l5,l6,l7,l8,l9,l10,l11'
set @units = '@label,@date,@hour,'+@units
;with cte as (select b.value,c.value as unit, a.orderCol as ri from dbo.explode(@s,';') a
cross apply dbo.explode(value,',') b
inner join dbo.explode(@units,',') c
    on b.orderCol = c.orderCol),
topCte as (
select c4.unit as unit
    ,convert(varchar,(case 
        when len(c3.value) <= 3 then '0' + substring(c3.value,1,1) + ':' + substring(c3.value,2,2) 
        else (substring(c3.value,1,2) + ':' + substring(c3.value,3,2))
        end+':00'),108) as [time]
    ,c1.value as label
    ,c2.value as [Date]
    ,c4.value
from cte c1
inner join cte c2
    on c1.ri = c2.ri and c1.unit = '@label' and c2.unit = '@date'
inner join cte c3
    on c1.ri = c3.ri and c3.unit = '@hour'
inner join cte c4
    on c1.ri = c4.ri and c4.unit not in ('@label','@date','@hour')
)
select unit, label, [date], value, cast([time] as time)
from topCte

这将失败：

消息 241，第 16 级，状态 1，第 5 行
从字符串转换日期和/或时间时转换失败。

但是，当我将最后两行更改为其中任何一行时，它都能正常工作：

select unit, label, [date], value, [time] 
from topCte

select unit, label, [date], cast([time] as time)
from topCte

我想强调的是，我完全意识到这段代码是次优的，并且我知道如何重新编写它，以便通过重写仍然满足业务需求的代码来避免错误。但是这个错误不应该以这种方式发生，我很好奇是什么触发了它。

Answer 1

我认为 SQL Server 运行上层查询的方式有问题。 我会将结果存储到临时表中，然后根据需要转换结果

create table #table_name
(
    unit varchar(3),
    label varchar(10),
    [date] varchar(10),
    value varchar(10),
    [time] varchar(10),
)


declare @s varchar(1000) = 'a,2015-10-08,1451,1,2,3,4,5,6,7,8,9,10,11;a,2015-10-08,1721,12,13,14,15,16,17,18,19,20,21,22'
declare @units varchar(1000) = 'l1,l2,l3,l4,l5,l6,l7,l8,l9,l10,l11'
set @units = '@label,@date,@hour,'+@units
;with cte as (select b.value,c.value as unit, a.orderCol as ri from dbo.explode(@s,';') a
cross apply dbo.explode(value,',') b
inner join dbo.explode(@units,',') c
    on b.orderCol = c.orderCol),
topCte as (
select c4.unit as unit
    ,(case 
        when len(c3.value) <= 3 then '0' + substring(c3.value,1,1) + ':' + substring(c3.value,2,2) 
        else (substring(c3.value,1,2) + ':' + substring(c3.value,3,2))
        end+':00') as [time]
    ,c1.value as label
    ,c2.value as [Date]
    ,c4.value
from cte c1
inner join cte c2
    on c1.ri = c2.ri and c1.unit = '@label' and c2.unit = '@date'
inner join cte c3
    on c1.ri = c3.ri and c3.unit = '@hour'
inner join cte c4
    on c1.ri = c4.ri and c4.unit not in ('@label','@date','@hour')
)
insert into #table_name(unit, label, [date], value, [time])
select unit, label, [date], value,  [time] 
from topCte

select unit, label, [date], value, cast([time] as time) 
from #table_name

Answer 2

问题是 [time] 列的大小写表达式。如果您在 select 语句中删除强制转换，您将看到像 14:51:00 这样对时间无效的值。您最初转换为 varchar 但未指定大小，这是另一个问题。确实没有必要将其转换为 varchar，因为它已经是 varchar 值。

这是您的代码的工作版本。

declare @s varchar(1000) = 'a,2015-10-08,1451,1,2,3,4,5,6,7,8,9,10,11;a,2015-10-08,1721,12,13,14,15,16,17,18,19,20,21,22'
declare @units varchar(1000) = 'l1,l2,l3,l4,l5,l6,l7,l8,l9,l10,l11'
set @units = '@label,@date,@hour,'+@units
;with cte as (select b.value,c.value as unit, a.orderCol as ri from dbo.explode(@s,';') a
cross apply dbo.explode(value,',') b
inner join dbo.explode(@units,',') c
    on b.orderCol = c.orderCol),
topCte as (
select c4.unit as unit
    ,
    case 
        when len(c3.value) <= 3 then '0' + substring(c3.value,1,1) + ':' + substring(c3.value,2,2) 
        else (substring(c3.value,1,2) + ':' + substring(c3.value,3,2))
        end
    as [time]

    ,c1.value as label
    ,c2.value as [Date]
    ,c4.value
from cte c1
inner join cte c2
    on c1.ri = c2.ri and c1.unit = '@label' and c2.unit = '@date'
inner join cte c3
    on c1.ri = c3.ri and c3.unit = '@hour'
inner join cte c4
    on c1.ri = c4.ri and c4.unit not in ('@label','@date','@hour')
)
select unit, label, [date], value, cast([time] as time)
from topCte