How to give a unique constraint to a combination of columns in Oracle?

sql oracle constraints unique-constraint composite-key

Create a unique key on those columns

ALTER TABLE YourTable  add CONSTRAINT YourTable_unique UNIQUE (B, C, D);

sql oracle constraints unique-constraint composite-key

First of all you should drop an existing Constraint by using below ALTER Query.

ALTER TABLE table_name   DROP CONSTRAINT myUniqueConstraint;

Now, you can create a UNIQUE Constraint by using the keyword UNIQUE with the combination of required Columns.

For Example:

ALTER TABLE table_name   ADD CONSTRAINT myUniqueConstraint UNIQUE(B, C, D);

sql oracle constraints unique-constraint composite-key

ALTER TABLE table_name DROP CONSTRAINT constraint_name;

CREATE UNIQUE INDEX constraint_name ON table_name(B,C,D)

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