A column set as the UNIQUE constraint column set for table_name. The columns must be defined as NOT NULL.
If you specify more than one column_name, the UNIQUE column set is based on the combined values of the specified column name.
For an unnamed UNIQUE table constraint, use this syntax:
ADD UNIQUE (column_name)
You cannot add a UNIQUE constraint on a column with the JSON data type.
- CONSTRAINT name
- For a named UNIQUE table constraint, use this syntax:
ADD CONSTRAINT constraint_name UNIQUE (column_name)
A UNIQUE table constraint can be defined on a maximum of 64 columns.