Combine multiple rows into one “memo” nvarchar(max)

问题

2 tables 1 with clients other with accno information

table 1:
file, accno <- nvarchar(50)
t1, 123a
t1, 456a
t1, 789a
t2, 012b
t3, 345c
t3, 678c

i would like to transfer table 1 to table 2

table 2:
file, accno <- nvarchar(max)
t1, 123a
    456a
    789a
t2, 012b
t3, 345c
    678c

i can do this is delphi very easy, but itll take forever almost 6 hrs because im filtering close to 300000 records on table 1

is there an sql query that can make this go super fast, even if it takes 5min

回答1:

SELECT
    DISTINCT [File]
    ,STUFF(
        (SELECT ',' + accno
        FROM
            TableName it
        WHERE it.[File] = ot.[File]
        FOR XML PATH(''))

        ,1,1,'') AS [Memo]
FROM
    TableName ot

You can adapt this but this will create a comma delimited list of your accno which I think is kind of what you are looking for? You can modify to do it with line endings in your Memo Field rather than commas.

回答2:

k so it turns out that the funny gizmozs on the ends was carriage returns, i managed to fix that by modifying query with the below

SELECT
    DISTINCT fileref, stuff(
        (
        Select '; ' + IsNull( D2.viaccno, '' )
        From vi_accno As D2
        Where D2.vifileref = A.FileRef
        For Xml Path(''), type
        ).value('.', 'nvarchar(max)')
        , 1, 2, '') As SelectedComments
FROM
   vtindex a

Thanks to @Matt for the help and response

来源：https://stackoverflow.com/questions/38087645/combine-multiple-rows-into-one-memo-nvarcharmax