SQL Server convert select a column and convert it to a string

Question

Is it possible to write a statement that selects a column from a table and converts the results to a string?

Ideally I would want to have comma separated values.

Answer 1

SELECT  CAST(<COLUMN Name> AS VARCHAR(3)) + ','
FROM    <TABLE Name>
FOR     XML PATH('')

Answer 2

The current accepted answer doesn't work for multiple groupings.
Try this when you need to operate on categories of column row-values.

Suppose I have the following data:

+---------+-----------+
| column1 |  column2  |
+---------+-----------+
| cat     | Felon     |
| cat     | Purz      |
| dog     | Fido      |
| dog     | Beethoven |
| dog     | Buddy     |
| bird    | Tweety    |
+---------+-----------+

And I want this as my output:

+------+----------------------+
| type |        names         |
+------+----------------------+
| cat  | Felon,Purz           |
| dog  | Fido,Beethoven,Buddy |
| bird | Tweety               |
+------+----------------------+

(If you're following along:

create table #column_to_list (column1 varchar(30), column2 varchar(30))
insert into #column_to_list
values 
('cat','Felon'),
('cat','Purz'),
('dog','Fido'),
('dog','Beethoven'),
('dog','Buddy'),
('bird','Tweety')

)

Now – I don’t want to go into all the syntax, but as you can see, this does the initial trick for us:

select ',' + cast(column2 as varchar(255)) as [text()]  
from #column_to_list sub
where column1 = 'dog'
for xml path('')
--Using "as [text()]" here is specific to the “for XML” line after our where clause and we can’t give a name to our selection, hence the weird column_name

output:

+------------------------------------------+
| XML_F52E2B61-18A1-11d1-B105-00805F49916B |
+------------------------------------------+
| ,Fido,Beethoven,Buddy                    |
+------------------------------------------+

You can see it’s limited in that it was for just one grouping (where column1 = ‘dog’) and it left a comma in the front, and additionally it’s named weird.

So, first let's handle the leading comma using the 'stuff' function and name our column stuff_list:

select stuff([list],1,1,'') as stuff_list
from (select ',' + cast(column2 as varchar(255)) as [text()]
         from #column_to_list sub
         where column1 = 'dog'
         for xml path('')
         ) sub_query([list]) 
--"sub_query([list])" just names our column as '[list]' so we can refer to it in the stuff function.  

Output:

+----------------------+
|      stuff_list      |
+----------------------+
| Fido,Beethoven,Buddy |
+----------------------+

Finally let’s just mush this into a select statement, noting the reference to the top_query alias defining which column1 we want (on the 5th line here):

select top_query.column1, 
          (select stuff([list],1,1,'') as stuff_list
         from (select ',' + cast(column2 as varchar(255)) as [text()]
                  from #column_to_list sub
                  where sub.column1 = top_query.column1
                  for xml path('')
                  ) sub_query([list])
              ) as pet_list
from  #column_to_list top_query
group by column1
order by column1

output:

+---------+----------------------+
| column1 |       pet_list       |
+---------+----------------------+
| bird    | Tweety               |
| cat     | Felon,Purz           |
| dog     | Fido,Beethoven,Buddy |
+---------+----------------------+

And we’re done.

You can read more here:

• FOR XML PATH in SQL server and [text()]
• https://docs.microsoft.com/en-us/sql/relational-databases/xml/use-path-mode-with-for-xml?view=sql-server-2017
• https://www.codeproject.com/Articles/691102/String-Aggregation-in-the-World-of-SQL-Server

Answer 3

Use simplest way of doing this-

SELECT GROUP_CONCAT(Column) from table

Answer 4

ALTER PROCEDURE [dbo].[spConvertir_CampoACadena]( @nomb_tabla   varchar(30),
                          @campo_tabla  varchar(30),
                          @delimitador  varchar(5),
                          @respuesta    varchar(max) OUTPUT
)
AS
DECLARE @query      varchar(1000),
    @cadena     varchar(500)
BEGIN
  SET @query = 'SELECT @cadena  = COALESCE(@cadena + '''+ @delimitador +''', '+ '''''' +') + '+ @campo_tabla + ' FROM '+@nomb_tabla
  --select @query
  EXEC(@query)
  SET @respuesta = @cadena  
END