For a column, a UNIQUE constraint specifies that the values in the column must be unique. For a table, the UNIQUE constraint identifies one or more columns that identify unique rows in the table. No two rows in the table can have the same values in all the named column(s). A table can have more than one UNIQUE constraint.

To manage unique constraints (Sybase Central)

1. Connect to the database as a user with DBA authority.

2. In the left pane, double-click Tables.

3. Click the table you want to alter.

4. In the right pane, click the Constraints tab.

5. Right-click in the Constraints tab and choose New » Unique Constraint.

6. Complete the instructions in the Create Unique Constraint Wizard.