Disjunctive subquery

Here it is a SQL query called from a .Net web service which is ”time outing” and to which I have been asked to bring a fix.

SELECT      d.col_id,
            d.col_no,
            d.col_dost_id,
            d.col_r_id,
            d.xxx,
            d.yyy,
            ……..
            d.zzz
      FROM table_mho d
      WHERE (d.COL_UK = ‘LRBRE-12052014’
          OR EXISTS (select 1
                     from table_mho d1
                     where d1.col_id = d.col_id
                       and exists (select 1
                                   from table_mho d2
                                   where d2.COL_UK = ‘LRBRE-12052014’
                                     and d1.master_col_id = d2.col_id
                                     and d2.col_type = 'M' )
                       and d1.col_type = 'S'
                       )
              )
    order by d.col_id;

Looking carefully at the content of this query I have immediately got a clue on what might be happening here: Disjunctive Subquery.

A disjunctive subquery represents a subquery that appears in an OR predicate (disjunction). 

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