--listagg(合并多行的值为字符串，只用一列来显示)

select status, count(*),  listagg(risk_id, ',') within group (order by risk_id) from rp_risk group by status;

select risk_id, status, listagg(risk_id, ',') within group (order by risk_id) over(partition by status) from rp_risk;

select risk.risk_id, listagg(officer.last_name || ',' || officer.first_name, '; ') within group(order by null) from rp_risk risk, rp_risk_area_ref re, rp_risk_area area, rp_risk_officer officer

where risk.risk_id = re.risk_id

and re.risk_area_id = area.risk_area_id(+)

and area.risk_officer_id = officer.risk_officer_id(+)

group by risk.risk_id;  

--pivot(行专列，将多行的值改为多列显示)(for in的那个column,是某个列的值，也就是将某个列的值作为新的列的column,这个column下边的值好像只能来自一列)

select * from

  (select risk.risk_id, re.risk_area_order, officer.last_name || ',' || officer.first_name fullname

  from rp_risk risk, rp_risk_area_ref re, rp_risk_area area, rp_risk_officer officer

  where risk.risk_id = re.risk_id

  and re.risk_area_id = area.risk_area_id(+)

  and area.risk_officer_id = officer.risk_officer_id(+) order by risk.risk_id desc, re.risk_area_order)

  pivot(max(fullname) for risk_area_order in (1 primaryOfficer, 2 addtionalOffcier1, 3 addtionalOffcier2)) order by risk_id desc;  

--decode(行专列，将多行的值改为多列显示)(decode的那个column,是某个列的值，也就是将某个列的值作为新的列的column,MAX聚集函数也可以用sum、min、avg等其他聚集函数替代)

select risk_id,

--max(decode(risk_area_order, 1, fullname)) primaryOfficer,

--max(decode(risk_area_order, 2, fullname)) addtionalOffcier1,

--max(decode(risk_area_order, 3, fullname)) addtionalOffcier1

min(decode(risk_area_order, 1, fullname)) primaryOfficer,

min(decode(risk_area_order, 2, fullname)) addtionalOffcier1,

min(decode(risk_area_order, 3, fullname)) addtionalOffcier1

from

  (select risk.risk_id, re.risk_area_order, officer.last_name || ',' || officer.first_name fullname from rp_risk risk, rp_risk_area_ref re, rp_risk_area area, rp_risk_officer officer

  where risk.risk_id = re.risk_id

  and re.risk_area_id = area.risk_area_id(+)

  and area.risk_officer_id = officer.risk_officer_id(+) order by risk.risk_id, re.risk_area_order)

group by risk_id order by risk_id;