一、表格:
CLASS CLASS_NAME PROFESSOR NUMBER_OF_STUDENTS COST START_DAT END_DATE ROO
----- -------------------- ------------------ ------------------ ---------- --------- --------- ---
PC102 Peripherals Henry Higgins 12 $1,100.00 11-JAN-13 11-MAY-13 129
PC101 MS OFFICE BASICS INDIANA JONES 18 $1,000.00 10-JAN-13 10-MAY-13 127
EE101 Elementary Education Frank McCourt 22 $900.00 12-JAN-13 12-MAY-13 227
PC123 MS OFFICE ADVANCED Bill Gates 10 $800.00 13-JAN-13 13-MAY-13 180
问题:
为学生人数添加检查约束以确保容量在 12 到 25 名学生之间。
我试过的
ALTER TABLE BW_CLASS
ADD CHECK( NUMBER_OF_STUDENTS > 15 AND
NUMBER_OF_STUDENTS < 25);
第 1 行返回 的错误:ORA-02293: 无法验证 (STUDENT.SYS_C007516) - 违反检查约束
我究竟做错了什么?