问SQL顶级oracle错误消息ORA-00902:无效的数据类型

EN

CREATE TABLE sessions 
(
    Ses_Start TIME NOT NULL,
    Ses_Finish TIME NOT NULL,
    A_ID NUMBER(2) NOT NULL,
    Vl_ID NUMBER(4) NOT NULL,
    Expense_per_head NUMBER(3) NOT NULL,

    CONSTRAINT pk_sessions PRIMARY KEY(A_ID, Vl_ID) 
);