PostgreSQL 10：使用此upsert函数，仅在列值不同时如何更新？

Question

我希望仅在apr不同的情况下进行更新，现在看来无论是否不同，它都将更新：

   INSERT INTO live_mytable (id, loan_type, apr, term, oldestyear) 
   SELECT id, loan_type, apr, term, oldestyear
   FROM   imp_mytable 
   ON CONFLICT (id,loan_type,term,oldestyear) DO update
   set apr = excluded.apr;

如何将查询更改为仅在值不同时才更新？

Answer 1

您可以在更新中使用WHERE子句：

 INSERT INTO live_mytable (id, loan_type, apr, term, oldestyear) 
   SELECT id, loan_type, apr, term, oldestyear
   FROM   imp_mytable 
 ON CONFLICT (id,loan_type,term,oldestyear) 
 DO update
   set apr = excluded.apr
 WHERE 
      live_mytable.apr IS DISTINCT FROM 
      EXCLUDED.apr;