case语句的使用

1.结合update的set使用：

UPDATE group_relation_station SET score_reduction=(CASEWHEN score_reduction < 100 THEN (score_reduction + 0.1) ELSE  100  END ), assessmentdate = now()  WHERE stationcode in  (select code from sensor_monitoring_stations s where s.id = new.station_id);

2.select中使用

BEGIN              UPDATE station_group_score_result  SET score_result= 100 WHERE score_result is null;               UPDATE station_group_score_result r, (SELECTorgid,CASEWHEN (100 - SUM(score_reduction)) < 0 THEN0ELSE(100 - SUM(score_reduction))END AS score_result_newFROMstation_groupGROUP BYorgid) scSET r.score_result = sc.score_result_newWHEREr.orgid = sc.orgid;END