Question

如何编写查询来更新我的行'S'。我想更新当前的主键以更改它的数量。我不确定我是否需要子查询。会更新分数，使用相同的方法更新“S”？ “S”表示学号，“C”表示课程号。

我尝试但失败的查询是

update grades set s = 114 where s = 100;

'set s'是我想要更新的内容，'where s'正在查找具有该set's'数字的行。对？

这是我的查询，触发器和从等级中选择*看起来像。

create table grades (
S varchar2(12),
C varchar2(10),
Score number(3,0),
Letter_Grade char(1),
Constraint pk_grades primary key (S),
Constraint CK_grades check (score between 0 and 100)
constraint lg_grades check (letter_grade  in ('A','B','C','D','F'))
);

SET SERVEROUTPUT ON
CREATE OR REPLACE TRIGGER MARK_BU
BEFORE UPDATE OF score ON grades
FOR EACH ROW
DECLARE
BEGIN
:NEW.letter_grade :=
 CASE 
    WHEN :NEW.score >= 80 THEN 'A'
    WHEN :NEW.score >= 70 THEN 'B'
    WHEN :NEW.score >= 60 THEN 'C'
    WHEN :NEW.score >= 50 THEN 'D'
   ELSE 'F'
END ;
DBMS_OUTPUT.PUT_LINE ('Numeric_grade was updated to:    ' || :NEW.score);
DBMS_OUTPUT.PUT_LINE ('Letter_grade was calculated to be:' || :NEW.letter_grade);
END;

S            C               SCORE L
------------ ---------- ---------- -
100          CST8255            49 F
101          CST8255            59 D
102          CST8255            69 C
103          CST8255            79 B
104          CST8255            89 A

Answer 1

update grades set s = 114 where s = 100;

是否正确可行。

如何使用Trigger更新Oracle中数据的数字行

1 个答案: