July 17, 2013 at 7:14 pm
This is puzzling.
I've run across a case where using between on string columns returns rows I'm not expecting. The following code will demonstrate the issue
declare @t table(Start varchar(10)
,[End] varchar(10))
insert @t
values('1500','1599')
,('2400','2799')
,('1','599')
,('2800','2999')
,('700','799')
,('A1','A3')
,('B4','B9')
declare @val varchar(10)
set @val = '2609'
select *
from @t
where @val between Start and [End]
I'm only expect to get 1 row back. But instead 2 rows are returning. Here's what is coming back..
StartEnd
24002799
1599
I can't figure out why the 1, 599 row is coming back. Does anybody have any ideas why this is happening?
Thanks!
July 17, 2013 at 8:51 pm
It's because the leading "2" falls between the leading "1" and the leading "5". You would need to LPAD the contents of the table and the string contained in @val to the same right justified length for it to work correctly.
--Jeff Moden
Change is inevitable... Change for the better is not.
July 17, 2013 at 9:00 pm
Here's your string example with the proper justification for jusing BETWEEN for such things. It returns the correct value, as expected.
declare @t table(Start varchar(10)
,[End] varchar(10))
insert @t
values('1500','1599')
,('2400','2799')
,(' 1',' 599')
,('2800','2999')
,(' 700',' 799')
,(' A1',' A3')
,(' B4',' B9')
declare @val varchar(10)
set @val = '2609'
select *
from @t
where @val between Start and [End]
Think of a dictionary because that's how strings work for this. If the "1" where an "A" and the "599" were "Egg", where would you the word "Bang" (your 2609) to appear even though it has more letters than either of the other 2? The same holds true for strings that look like numbers.
--Jeff Moden
Change is inevitable... Change for the better is not.
July 17, 2013 at 9:24 pm
Interesting, this is probably context specific, but how does SQL deal with the alphanumeric "numbers" in that table? Say we pad all the values and choose an @val which is in the middle of one of the "Hex Looking" values.
declare @t table(Start varchar(10)
,[End] varchar(10))
insert @t
values('1500','1599')
,('2400','2799')
,('0001','0599')
,('2800','2999')
,('0700','0799')
,('00A1','00A3')
,('00B4','00B9')
declare @val varchar(10)
set @val = '00A2'
select *
from @t
where @val between Start and [end]
We get back 2 rows:
Start End
00010599
00A100A3[/CODE]
I'm sure we're looking at the same thing come into play, but would there be any value in doing some conversion to a common format with the strings? Are they even supposed to be in the same base?
Edit: getting the same results padding with spaces too.
Think of a dictionary because that's how strings work for this. If the "1" where an "A" and the "599" were "Egg", where would you the word "Bang" (your 2609) to appear even though it has more letters than either of the other 2? The same holds true for strings that look like numbers.
Good explanation, most of this post can probably be ignored. I think I'm just worried by the fact that the data seems inconsistent for the purpose of the example 😛
July 17, 2013 at 10:52 pm
Thanks! I must have total spaced. I should have know why that was happening.
I liked the idea with padding with spaces but if I tried to use @val=2 then nothing would come back. I would have to know how many spaces to pad @val with. Paddding with 0s doesn't solve it either.
So here's what I came up with
declare @t table(Start varchar(10)
,[End] varchar(10)
,StartLen as len(Start)
,EndLen as len([End]))
insert @t
values('1500','1599')
,('2400','2799')
,('1','599')
,('2800','2999')
,('700','799')
,('A1','A3')
,('B4','B9')
declare @val varchar(10)
set @val = '2609'
select *
from @t
where @val between Start and [End]
and len(@val) between StartLen and EndLen
This seems to do the trick.
The actual table is pretty static. It's only updated a few times a year. I'll play around with adding an index on the computed columns to see if that gives any performance benefit.
Thanks!
July 18, 2013 at 11:33 am
You can pad the string values for proper sorting using the REPLICATE operator.
For example:
DECLARE @val VARCHAR(10)
SET @val = '2609'
DECLARE @t TABLE
(
[Start] VARCHAR(10)
,[End] VARCHAR(10)
)
INSERT @t
VALUES
('1500','1599')
, ('2400','2799')
, ('1','599')
, ('2800','2999')
, ('700','799')
, ('A1','A3')
, ('B4','B9')
SELECT
Start
,[End]
FROM
@t
WHERE
@val BETWEEN [Start] AND [End]
Your output:
StartEnd
24002799
1599
SELECT
r.[Start]
,r.[End]
FROM
(
SELECT
[Start]+REPLICATE('0',6-LEN([Start])) AS [Start]
,[End]+REPLICATE('0',6-LEN([End])) AS [End]
FROM
@t
) r
WHERE
@val BETWEEN [Start] AND [End]
Output padded right:
StartEnd
240000279900
100000599000
SET @val = '002609'
SELECT
r.[Start]
,r.[End]
FROM
(
SELECT
REPLICATE('0',6-LEN([Start]))+[Start] AS [Start]
,REPLICATE('0',6-LEN([End]))+[End] AS [End]
FROM
@t
) r
WHERE
@val BETWEEN [Start] AND [End]
Output padded left:
StartEnd
002400002799
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