Oracle Database Discussions

Hi,
I drop constraints for the table using syntax:

ALTER TABLE TB_TEST DROP CONSTRAINT TB_CONS_TEST;
Table altered
Then,i add constraint for the object with same unique constraint name

ALTER TABLE TB_TEST ADD CONSTRAINT TB_CONS_TEST UNIQUE
(COMPANY_CODE,
LOB_CODE,
DIVISION_CODE,
BU_CODE,
GROUP_ID,
ACCT_CODE,
BRANCH_CODE,
);
iam getting the error: ora-00955 name is already used by an existing object

If I use the different name then it is succeding. why I can't use the same name since I dropped it already

Regards,
Faiz