I need help with my SQL code. How do i add a unique constraint to a table?

[uwemneku]

I ran the following SQL code

-- create a table
CREATE TABLE DEPT (
  ID NUMBER(7) PRIMARY KEY,
  NAME VARCHAR2(25)
);
-- -- insert some values
INSERT INTO DEPT (ID , NAME) VALUES  (40, 'Sales') ;   

ALTER TABLE DEPT ADD Manager_ID NUMBER(5) ;
ALTER TABLE DEPT ADD City VARCHAR2(30);

This works fine but when i try to add a unique constraint to the city column with the following command

ALTER TABLE DEPT
ADD CONSTRAINT UC_ffg UNIQUE(city);

I get the following error
1 near “CONSTRAINT”: syntax error

How can i add a unique constraint to a column

[chichkenmomos]

capitalize the “C” in City. SQL is case sensitive when it comes to tables and column names

[helanyu123]

Just a reminder, if your table has some data that doesn’t fit the constraints you gonna add, you will get an error.