If the clause is not specified, a unique constraint name is generated by the database manager.
Each column-name must be an unqualified name that identifies a column of the table. The same column must not be identified more than once. The column must not be a LOB or DATALINK column. The number of identified columns must not exceed 120, and the sum of their byte counts must not exceed 32766-n, where n is the number of columns specified that allow nulls. For information on byte-counts see Table 52.
The unique index is created as part of the system physical file, not a separate system logical file. When a primary key is added, a CHECK constraint is implicitly added to enforce the rule that the NULL value is not allowed in any of the columns that make up the primary key.
Each column-name must be an unqualified name that identifies a column of the table. The same column must not be identified more than once. The column must not be a LOB or DATALINK column. The number of identified columns must not exceed 120, and the sum of their byte counts must not exceed 32766-n, where n is the number of columns specified that allows nulls. For information on byte-counts see Table 52.
A unique index on the identified column is created during the execution of the CREATE TABLE statement. The unique index is created as part of the system physical file, not as a separate system logical file.
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