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

Question

I encountered a weird error in our SQL Server 2008 R2 server. The cast of a varchar to time fails depending on what other columns are used in SELECT clause of the top level statement. Code to reproduce the issue

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

And the query:

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

This will fail with:

Msg 241, Level 16, State 1, Line 5
Conversion failed when converting date and/or time from character string.

However when I change the last two lines into any of these, it works correctly:

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

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

I would like to stress that I'm fully aware that this code is sub optimal and I know how to rework this so to avoid the error by rewriting the code still fullfilling business requirement. However this error shouldn't occur in this way and I'm very curious what is triggering it.

Answer 1

I believe there is something wrong in how SQL Server runs the upper query. I would store the result into a Temporary Table and then cast the result as desired

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

The problem is your case expression for the [time] column. If you remove the cast in the select statement you will see values like 14:51:00 which is invalid for time. You are initially converting to a varchar but you don't specify the size which is another issue. There really is no need to convert this to a varchar because it is already a varchar value.

Here is a working version of your code.

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