创建如下表数据 select * from t1 ; select * from t2;
现需求：参照T2表，修改T1表，修改条件为两表的fname列内容一致。 16.1 方式1，update UPDATE T1 SET T1.FMONEY = (select T2.FMONEY from t2 where T2.FNAME = T1.FNAME) WHERE EXISTS(SELECT 1 FROM T2 WHERE T2.FNAME = T1.FNAME);
实例：更新 PURCHASE_CONTRACT表中预算主体BUDGETSUBJECT ，参照 PURCHASE_CONTRACT1 UPDATE PURCHASE_CONTRACT T1 SET T1.BUDGETSUBJECT = (select T2.BUDGETSUBJECT from PURCHASE_CONTRACT1 T2 where T2.ID = T1.ID) WHERE EXISTS(SELECT 1 FROM PURCHASE_CONTRACT1 T2 WHERE T2.ID = T1.ID) AND T1.BUDGETSUBJECT IS NULL
