Question

I have a query below:

select col1,
       col2,
       .
       .
       .
       coln
  from table1
  left join table2
  on some condition
  .
  .
  left  join tablen
  on some condition
  left join (
              select t1.col1,
              (
                select t2.col2 + ';' as [data()]
                  from SomeTable t2
                 where t2.col1 = t1.col1
                 for xml path('')
              ) value
              from SomeTable t1
              group by t1.Col1
            )MyTable
         on some condition

The above query will return about 4000 rows. The inline select statement using xml path will also result in about 4000 records.

I wish to know if there will be any performance impact with this query due to the use of xml path.

Thanks in advance.

Answer 1

Unless and untill you have proper indexes on the all joining columns in left join and proper covering indexes in select list of columns,there wont be any performance issue here.