Convert image datatype into varchar in sql server 2008

Question

We have TestPartner database in SQL Server. The descriptions of the bugs are stored in \"image\" datatype column. We need to write a query to display the data as html table. We

Answer 1

You can convert also like this

convert (varchar(max) , convert (varbinary (max) , blob_data)), cast(cast(blob_data as binary) as varchar(max)) 

Answer 2

If the data has been stored in the image field as Unicode data, it won't work if you replace the line Select CONVERT(nvarchar(1000), convert(varbinary(1000), tpcommanddetail)) From TestPartnerDB.TP_RESULTS_RECORDS with Select CONVERT(varchar(1000), convert(varbinary(1000), tpcommanddetail)) From TestPartnerDB.TP_RESULTS_RECORDS.

It's very important that the first conversion from binary data to text be made with the right collation and size of characters: if the text is in Ascii, you must use varchar() and if the text is in Unicode, you must use nvarchar().

The second conversion from nvarchar(100) to varchar(100) looks useless to me.

The use of binary(100) instead of varbinary(100) looks also very suspicious to me.

Finally, if you get strange characters like 0x0002 then maybe this is why that this has been stored in an image field instead of a text field: this is a specially formated field where not all characters are text characters. However, as you didn't show us the result of printing the original field in binary (or more exactly, in hexadecimal) or of any of your results, it's impossible to say anything more.

I've just cooked up a few tests; with these, you should be able to understand what's happening:

select ascii ('A'), unicode(N'A');
select convert (binary(2), ascii('A')), convert (binary(2), unicode(N'A'));
--
declare @ab binary(10), @vab varbinary(10);
declare @nab binary(10), @vnab varbinary(10);
--
set @ab = convert (binary (10), 'AB');
set @vab = convert (varbinary (10), 'AB');
set @nab = convert (binary (10), N'AB');
set @vnab = convert (varbinary (10), N'AB');
--
select @ab, @vab, @nab, @vnab;
--
select convert(varchar(10), @ab) + '*', 
    convert(varchar(10), @vab) + '*', 
    convert(varchar(10), @nab) + '*', 
    convert(varchar(10), @vnab) + '*';
--
select len(convert(varchar(10), @ab)), 
    len(convert(varchar(10), @vab)), 
    len(convert(varchar(10), @nab)), 
    len(convert(varchar(10), @vnab));
--
select len(convert(varchar(10), @ab) + '*'), 
    len(convert(varchar(10), @vab) + '*'), 
    len(convert(varchar(10), @nab) + '*'), 
    len(convert(varchar(10), @vnab) + '*');
--
select convert(nvarchar(10), @ab) + '*', 
    convert(nvarchar(10), @vab) + '*', 
    convert(nvarchar(10), @nab) + '*', 
    convert(nvarchar(10), @vnab) + '*';
--
select len(convert(nvarchar(10), @ab)), 
    len(convert(nvarchar(10), @vab)), 
    len(convert(nvarchar(10), @nab)), 
    len(convert(nvarchar(10), @vnab));
--
select convert(varchar(10), convert(nvarchar(10), @ab)) + '*', 
    convert(varchar(10), convert(nvarchar(10), @vab)) + '*', 
    convert(varchar(10), convert(nvarchar(10), @nab)) + '*', 
    convert(varchar(10), convert(nvarchar(10), @vnab)) + '*';
--
select len(convert(varchar(10), convert(nvarchar(10), @ab))), 
    len(convert(varchar(10), convert(nvarchar(10), @vab))), 
    len(convert(varchar(10), convert(nvarchar(10), @nab))), 
    len(convert(varchar(10), convert(nvarchar(10), @vnab)));
--
select convert(nvarchar(10), @nab) for xml path('tr');
select convert(varchar(10), convert(nvarchar(10), @nab)) for xml path('tr');
select 'The Name' as td, '', convert(nvarchar(10), @nab) as td for xml path('tr');

Answer 3

My guess would be that the data stored in your image column is not 'normal' text - I would guess that it's some arbitrary data structure (hence the decision to use image rather than varchar) ?

I tried this without a problem:

    declare @data varchar(max)

    declare @fred table (d1 varchar(max), d2 xml, d3 image)

    set @data = 'here is some data'
    while (len(@data) < 200)    set @data = @data + ' ' + cast(rand() as varchar)

    insert into @fred (d1,d2,d3) values (@data,@data,@data)

    set @data = 'here is some more data'
    while (len(@data) < 200)    set @data = @data + ' ' + cast(rand() as varchar)

    insert into @fred (d1,d2,d3) values (@data,@data,@data)

    declare @xml xml
    set @xml = (select cast(cast(d3 as varbinary(max)) as varchar(max)) as 'td' from @fred FOR XML PATH('tr'), TYPE)

    select @xml

Answer 4

Try this code:

Select  MASTER.dbo.Fn_varbintohexstr(tpcommanddetail) From TestPartnerDB.TP_RESULTS_RECORDS

Answer 5

The simple answer is

select cast(cast(my_column as varbinary(max)) as varchar(max)) as column_name
from   my_table

This converts the column to varchar format. nvarchar(max) might be better if you have unicode data.