1 create table topic 2 ( 3 tid number 4 constraint pk_tid primary key, 5 tsid number 6 constraint fk_tsid references section(sid), 7 tuid number 8 constraint fk_tuid references users(uid1), 9 treplycount number default 0, 10 tface number, 11 ttopic varchar2(20) not null, 12 tcontents varchar2(20) 13 constraint ck_tcontents check(length(tcontents)>6), 14 ttime date default sysdate, 15 tclickcount number default 0, 16 tstate number default 1, 17 tlasreply date 18 constraint ck_tlasreply check(constraint>ttime) 19* )SQL> /)*第 19 行出现错误:ORA-02438: 列检查约束条件无法引用其它列