PG数据库实现merge into方法

语法格式1：有则更新，无则插入

insert into table_1(column_1,column_2, column_3)
select column_1,
       column_2,
       column_3,
  from table_2
    on conflict (column_1)
	do update set
    column_2 = excluded.column_2,
	column_3 = excluded.column_3

如：

insert into ua_cj_assess_result(id,all_analysis)
select id,
       (lte_health_assess+nr_health_assess)/2 as all_analysis
  from ua_cj_assess_result a
    on conflict (id)
	do update set
    all_analysis = excluded.all_analysis

语法格式2：有则不操作，无则插入

insert into table_1(column_1,column_2, column_3)
select column_1,
       column_2,
       column_3
  from table_2
    on conflict (column_1)
	do nothing

注意事项：
1、conflict 里的字段必须是主键
2、关联字段必须在表中字段顺序的第一个位置
3、select出来的字段名称必须和目标表中的字段名称一致