Can I add a UNIQUE constraint to a PostgreSQL table, after it's already created?

Question

I have the following table:

 tickername | tickerbbname  | tickertype
------------+---------------+------------
 USDZAR     | USDZAR Curncy | C
 EURCZK     |          


        

Answer 1

psql's inline help:

\h ALTER TABLE

Also documented in the postgres docs (an excellent resource, plus easy to read, too).

ALTER TABLE tablename ADD CONSTRAINT constraintname UNIQUE (columns);