Is it possible to use unique on multiple columns?
like:
user_vote user_id
------------------
1 1
1 2
2 1
both unique
This must be possible
But:
user_vote user_id
1 2
1 2
This must not be possible
You can add a unique constraint on the column's combination:
ALTER TABLE my_table
ADD CONSTRAINT my_table_uq UNIQUE (user_vote, user_id)
CREATE TABLE uservotetable
(
user_vote int NOT NULL,
user_id int NOT NULL,
CONSTRAINT uservote UNIQUE (user_vote ,user_id)
);
and if you created your table before ..then you can use ALTER
ALTER TABLE uservotetable
ADD CONSTRAINT uservote UNIQUE (user_vote ,user_id)
this can be useful for you sql_unique
You need to define a composite unique constraint.
SQL Server, One way to do that in SQL Server is by adding UNIQUE INDEX
ALTER TABLE table_name ADD UNIQUE INDEX (User_Vote, User_Id);
In Oracle,
ALTER TABLE table_name
ADD CONSTRAINT uc_1 UNIQUE (User_Vote, User_Id)
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