Oracle combines multiple rows of data into one row of data

Preface

When I was paddling, I saw someone ask this question , Write a handy sql Make a note of .

primary sql data （ Multiple lines ）

select null as v1_name, 1 as v1, ' name 2' as v2_name, 2 as v2
  from dual
union all
select ' name 3' as v1_name, 3 as v1, ' name 4' as v2_name, 4 as v2
  from dual

After the merger

select (wm_concat(a.v1_name)) as v1_name,
       (wm_concat(a.v1)) as v1,
       (wm_concat(a.v2_name)) as v2_name,
       (wm_concat(a.v2)) as v2
  from (select null as v1_name, 1 as v1, ' name 2' as v2_name, 2 as v2
          from dual
        union all
        select ' name 3' as v1_name, 3 as v1, ' name 4' as v2_name, 4 as v2
          from dual) a