How to read a text file
I've inherited a horrible stored proc to load an XSL file from a text file into one TEXT column in one row. It BULK INSERTs into a temporary table and then cursors through that somehow appending the lines together into a TEXT variable using TEXTPTR and UPDATETEXT. The whole thing is in a transaction. What could go wrong?
Well, it's suddenly started occasionally not loading some of the start of the file. No errors, it just sometimes misses off the first n bytes (always the same number of bytes).
I have a recipe like this that works:
create table #FileContents
(
LineNumber int identity
, LineContents nvarchar(4000)
);
declare @FileName varchar(255);
declare @NewLine char(2) = char(13) + char(10);
declare @CmdLine varchar(300);
declare @XSL varchar(max);
set @FileName = ''
set @CmdLine = 'type ' + @FileName;
insert #FileContents
exec master.dbo.xp_cmdshell @CmdLine;
select @XSL = isnull(@XSL, '') + @NewLine + isnull(LineContents, '')
from #FileContents
order by LineNumber;
Is there a cleaner way? Maybe one that doesn't use xp_cmdshell?
Best Answer
Here is the sample showing how to insert the guts of the file to the table without using the xp_cmdshell:
create table #FileContents
(
LineNumber int identity (1, 1),
LineContents nvarchar(4000)
);
insert into #FileContents
select f.BulkColumn
from openrowset
(
bulk 'C:\Useless\Temp\some_file.txt',
single_clob
) f;
select * from #FileContents;
The results display (because this what was in the file):
LineNumber LineContents
----------- ------------
1 Hello, Jerry
Hello, Newman
Of course it goes without saying that the file path is relative to the server.
Oleg
@David Wimbush Thank you. In my answer, the path to the file is hardcoded because openrowset will not accept a path as a parameter. This means that should the file path be a parameter, the **insert into select from** should be spelled out into a varchar variable which can be fed to the execute in order to bypass this limitation of the openrowset. For example,
declare @file_path nvarchar(50);
-- declare the size as needed (no limit)
declare @sql nvarchar(500);
select
@file_path = 'C:\\Useless\\Temp\\some_file.txt',
@sql = 'insert into #FileContents
select f.BulkColumn
from openrowset
(
bulk ''' + @file_path + ''',
single_clob
) f;';
exec (@sql);So I discovered! But you put me on the right track. Thanks.
If you can create a CLR assembly with EXTERNAL_ACCESS, then I would go that route. Given that you have a nvarchar(4000) column, you will want to split larger text files into smaller chunks.
You will also want it not to epic fail on Unicode.
A CLR table function could be a neat way to achieve the above two without causing the massive hole that xp_cmdshell does.
Thanks Matt. +1 because I think this is probably the technically superior solution. But this is a live problem a quick fix is needed so I'm going with Oleg's answer in this case.
@David Wimbush - fair play - but do remember that if you need Unicode support (which the nvarchar suggests) then you will need to do it properly...
@Matt Whitfield +1 This is a very sound solution! As a matter of fact, you gave me an excellent idea on the task I am working right now. Thank you.
