when I create a table like this:
create table DBDI_HIREDETAIL(
HireID int not null,
EquipID int not null,
Error at Command Line: "TotalFee float"
SQL Error: ORA-00904: : invalid identifier
00904. 00000 - "%s: invalid identifier"
COMMENT is a reserved word in Oracle; it's used for adding comments to the data dictionary. You should avoid using this as a column name.
SQL> create table a ( comment number ); create table a ( comment number ) * ERROR at line 1: ORA-00904: : invalid identifier
If you really want to use this column name you're have to quote it, i.e.
SQL> create table a ( "COMMENT" number ); Table created.
I would recommend you not doing this as you have to quote the column everywhere.