Parse SQL field into multiple rows - sql

Question

How can I take a SQL table that looks like this:
MemberNumber JoinDate Associate
1234 1/1/2011 A1 free A2 upgrade A31
5678 3/15/2011 A4
9012 5/10/2011 free
And output (using a view or writing to another table or whatever is easiest) this:
MemberNumber Date
1234-P 1/1/2011
1234-A1 1/1/2011
1234-A2 1/1/2011
1234-A31 1/1/2011
5678-P 3/15/2011
5678-A4 3/15/2011
9012-P 5/10/2011
Where each row results in a "-P" (primary) output line as well as any A# (associate) lines. The Associate field can contain a number of different non-"A#" values, but the "A#"s are all I'm interested in (# is from 1 to 99). There can be many "A#"s in that one field too.

Answer 1

Of course a table redesign would greatly simplify this query but sometimes we just need to get it done. I wrote the below query using multiple CTEs; I find its easier to follow and see exactly whats going on, but you could simplify this further once you grasp the technique.
To inject your "P" primary row you will see that I simply jammed it into Associate column but it might be better placed in a simple UNION outside the CTEs.
In addition, if you do choose to refactor your schema the below technique can be used to "split" your Associate column into rows.
;with
Split (MemberNumber, JoinDate, AssociateItem)
as ( select MemberNumber, JoinDate, p.n.value('(./text())[1]','varchar(25)')
from ( select MemberNumber, JoinDate, n=cast('<n>'+replace(Associate + ' P',' ','</n><n>')+'</n>' as xml).query('.')
from #t
) a
cross apply n.nodes('n') p(n)
)
select MemberNumber + '-' + AssociateItem,
JoinDate
from Split
where left(AssociateItem, 1) in ('A','P')
order
by MemberNumber;
The XML method is not a great option performance-wise, as its speed degrades as the number of items in the "array" increases. If you have long arrays the follow approach might be of use to you:
--* should be physical table, but use this cte if needed
--;with
--number (n)
--as ( select top(50) row_number() over(order by number) as n
-- from master..spt_values
-- )
select MemberNumber + '-' + substring(Associate, n, isnull(nullif(charindex(' ', Associate + ' P', n)-1, -1), len(Associate)) - n+1),
JoinDate
from ( select MemberNumber, JoinDate, Associate + ' P' from #t
) t (MemberNumber, JoinDate, Associate)
cross
apply number n
where n <= convert(int, len(Associate)) and
substring(' ' + Associate, n, 1) = ' ' and
left(substring(Associate, n, isnull(nullif(charindex(' ', Associate, n)-1, -1), len(Associate)) - n+1), 1) in ('A', 'P');

Answer 2

Try this new version
declare #t table (MemberNumber varchar(8), JoinDate date, Associate varchar(50))
insert into #t values ('1234', '1/1/2011', 'A1 free A2 upgrade A31'),('5678', '3/15/2011', 'A4'),('9012', '5/10/2011', 'free')
;with b(f, t, membernumber, joindate, associate)
as
(
select 1, 0, membernumber, joindate, Associate
from #t
union all
select t+1, charindex(' ',Associate + ' ', t+1), membernumber, joindate, Associate
from b
where t < len(Associate)
)
select MemberNumber + case when t = 0 then '-P' else '-'+substring(Associate, f,t-f) end NewMemberNumber, JoinDate
from b
where t = 0 or substring(Associate, f,1) = 'A'
--where t = 0 or substring(Associate, f,2) like 'A[1-9]'
-- order by MemberNumber, t
Result is the same as the requested output.

Answer 3

I would recommend altering your database structure by adding a link table instead of the "Associate" column. A link table would consist of two or more columns like this:
MemberNumber Associate Details
-----------------------------------
1234 A1 free
1234 A2 upgrade
1234 A31
5678 A4
Then the desired result can be obtained with a simple JOIN:
SELECT CONCAT(m.`MemberNumber`, '-', 'P'), m.`JoinDate`
FROM `members` m
UNION
SELECT CONCAT(m.`MemberNumber`, '-', IFNULL(a.`Associate`, 'P')), m.`JoinDate`
FROM `members` m
RIGHT JOIN `members_associates` a ON m.`MemberNumber` = a.`MemberNumber`