postgresql - PostgreSQL 10：使用这个 upsert 函数，只有当列值不同时如何更新？

Question

我只想apr在它不同时才更新，现在，无论它是不同还是相同，它看起来都会更新：

   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;

如果值不同，如何将此查询更改为仅更新？

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;