循环遍历sql（SQL或Asp.net C＃）的最佳方法是什么？

Question

I am creating a list to send an e-mail to. The individual who is logged in has a field in the database of who they report to (unless there is an error or they report to no one).

So for instance if I am logged in and clicked the submit button in SQL it would say I report to 'John Doe'

I then need to grab who 'John Doe' reports to and add that to the list. I need to keep climbing the list until we reach the top of the company (the GID will be blank or null).

Using me as an example, I report to 'John Doe' who reports to 'Tom Doe' . Tom reports to no-one his usrReportsTo field is like this '00000000-0000-0000-0000-000000000000' .

If the usrReportsTo field is "" or NULL or '00000000-0000-0000-0000-000000000000' the loop should terminate.

Here is the sql I used.

What is the cleanest/neatest/most effecient way to perform this loop and is it better to do it in SQL or ASP.net C#?

select usrReportsTo from dbo.CVT_Users_usr, usrEmailAddress
WHERE RTRIM(usrFirstName) + ' ' + RTRIM(usrLastName) = 'James Wilson' 
-- Returns 'James Wilson' + email

SELECT RTRIM(usrFirstName) + ' ' + RTRIM(usrLastName) as Name, usrEmailAddress, usrReportsTo from dbo.CVT_Users_usr
WHERE usrGID = '38922F83-4B6E-499E-BF4F-EF0B094F47F7'
-- Returns 'John Doe' + email + reportsTo

SELECT RTRIM(usrFirstName) + ' ' + RTRIM(usrLastName) as Name, usrEmailAddress, usrReportsTo from dbo.CVT_Users_usr
WHERE usrGID = 'FB8F4939-3956-4834-9D89-D72AFB8BF3E0'
-- Returns 'Tom Doe' + email + reportsTo

Edit #3

Working copy of SQL just doesn't return 100% true data.

with cte AS ( select usrGID, RTRIM(usrFirstName) + ' ' + RTRIM(usrLastName) as Name, usrEmailAddress, usrReportsTo from dbo.CVT_Users_usr union all select u.usrGID, RTRIM(u.usrFirstName) + ' ' + RTRIM(u.usrLastName), cte.usrEmailAddress, cte.usrReportsTo from dbo.CVT_Users_usr u inner join cte on u.usrReportsTo = cte.usrGID ) select * from cte where Name = 'James Wilson'

-- Returns

usrGID Name usrEmailAddress usrReportsTo E1DAFC11-BE35-4730-9961-68EEF8D85DE4 James Wilson 38922F83-4B6E-499E-BF4F-EF0B094F47F7 E1DAFC11-BE35-4730-9961-68EEF8D85DE4 James Wilson john@1234.com FB8F4939-3956-4834-9D89-D72AFB8BF3E0 E1DAFC11-BE35-4730-9961-68EEF8D85DE4 James Wilson tom@1234.com 00000000-0000-0000-0000-000000000000

Shouldn't the usrGID and name match the same way usrEmailAddress and usrReportsTo does? I tried chaanging the sql to be cte.USRGID and cte.Name but it gave the max recursion error.

Any ideas?

Answer 1

Using a common table expression you can generate the complete result set in one SQL statement (via a recursive join), thus avoiding any looping at all.

A basic example with the key fields

create table #CVT_Users_usr (usrGid uniqueidentifier, usrEmailAddress varchar(50), usrFirstName varchar(20), usrLastName varchar(20), usrReportsTo uniqueidentifier)

insert #CVT_Users_usr values    
('38922F83-4B6E-499E-BF4F-EF0B094F47F7' , 'james@wilson.com','james','wilson', 'E1DAFC11-BE35-4730-9961-68EEF8D85DE4'),
('E1DAFC11-BE35-4730-9961-68EEF8D85DE4', 'john@doe.com','john','doe', 'FB8F4939-3956-4834-9D89-D72AFB8BF3E0'),
('FB8F4939-3956-4834-9D89-D72AFB8BF3E0', 'tom@doe.com','tom','doe' ,'00000000-0000-0000-0000-000000000000'),
('FE6899A5-63BA-42B7-A70E-011711A5FAC6', 'ken@ken.com','ken', 'kenneths', 'FB8F4939-3956-4834-9D89-D72AFB8BF3E0')

declare @id uniqueidentifier
select @id = usrGid from #CVT_Users_usr where usrFirstName='james' and usrLastName='wilson'

;with cte as
(
select usrGid, usrEmailAddress, usrFirstName, usrLastName, usrReportsTo from #CVT_Users_usr
union all
select u.usrGid,  cte.usrEmailAddress, cte.usrFirstName, cte.usrLastName, cte.usrReportsTo 
from #CVT_Users_usr u
    inner join cte on u.usrReportsTo= cte.usrGid
)
    select usrFirstName + ' ' + usrLastName, usrEmailAddress  from cte
    where usrGid=@id

drop table #CVT_Users_usr