Please note : This help page is not for the latest version of Enterprise Architect. The latest help can be found here.
Unique Constraints
Unique constraints are a combination of values (represented by Table columns) that uniquely identify a row in the Table. You can have several unique constraints in a Table, one of which can be separately identified as the Primary Key of the Table.
Access In diagram or Project Browser | Right-click on Table | Features & Properties | Operations > Constraint | Add New Constraint (Ctrl+N)
Create a Constraint
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1 |
On the Constraint tab of the Columns and Constraints screen, a new constraint is automatically created and assigned the default constraint name and a Type of index. Overtype the constraint name with a name that identifies this as a unique constraint.
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2 |
In the Type field, change the value from index to unique.
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3 |
If you prefer, type an alias for the constraint, in the Alias field. The Columns field is read-only; it is populated with the columns that you assign to the Involved Columns tab (step 4).
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4 |
The Available Columns panel lists the columns defined for the Table (on the Columns tab). For each column to assign to the constraint, either:
The column name is transferred to the Involved Columns tab.
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5 |
If you do not want the assigned column in the Involved Columns tab, either:
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6 |
If you have a number of columns in the constraint, you can rearrange the sequence by right-clicking on the column to move and selecting either:
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7 |
If necessary, you can type a formatted comment in the field on the Notes tab.
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8 |
(On the Columns and Constraints dialog) Click on the Close button.
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Delete a unique constraint
If you do not want to keep a unique constraint, either:
| · | Right-click on it in the list and select Delete constraint '<name>', or |
| · | Click on the item and press Ctrl+D |
The constraint is immediately deleted.
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