Question

I want to store data from multiple tables into one table

table A (
p, q,
PRIMARY KEY (p,q)
)

table B (
p, m, n,
PRIMARY KEY (p,m,n)
)

table output(
p,
xml
)

The output should be like

for table A

 -------------------------------
|    p      |        xml        |
---------------------------------
|value of p | <q>some value</q> |
 -------------------------------

for table B

 -----------------------------------------------
|    p      |        xml                        |
------------------------------------------------
|value of p | <m>some value</m><n>some data</n> |
 -----------------------------------------------

This can be achieved by this query

SELECT * 
FROM Students s
CROSS APPLY
(
    SELECT 
        (
            SELECT * 
            FROM Students t
            WHERE t.DisplayName = s.DisplayName
            FOR XML RAW
        ) x1
)x

But I want to make the SQL generic enough so that given any table name we can get the above output.

The problem with the inner join is that then the query will not be generic

Answer 1

To get the result you want from one table you could use something like this:

select T.Table1ID,
       (
         select T.*
         for xml raw, type
       ) as x1
from Table1 as T

To apply the same pattern to another table you need to change the table name and the field name of the key column.

select T.Table2ID,
       (
         select T.*
         for xml raw, type
       ) as x1
from Table2 as T

If you want a even more generic version you can use dynamic SQL and build your query from a table name and a column name.

declare @TableName sysname 
declare @KeyColumnName sysname

set @TableName = 'master..spt_values'
set @KeyColumnName = 'Number'

declare @SQL nvarchar(500)

set @SQL = '
select '+@KeyColumnName+',
       (
         select T.*
         for xml raw, type
       ) as x1
from '+@TableName+' as T'

exec (@SQL)