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Tip #4 – How to Make a Column Unique

Sometimes there are columns in a table that don’t belong to primary key, but are still unique. To mark them as a unique, you have to create an alternate (unique) key containing it.

Single-column alternate (unique) key

Select the table with the column you want to make a unique. Then, click the Alternate (unique) key tab in the Table properties panel on the right:

Select the table containing the column you want to make a unique. Then, expand the ‘Alternate (unique) key’ section in the ‘Table properties’ panel on the right

Click Add key:

Click 'Add key', alternate key

Click the down arrow to show the properties:

Click the down arrow to show the properties, alternate key

Find the column you want to make a unique and add it to the key:

Find the right column and add it to the key, unique column

Now, the column is unique:

Now, the column is set as unique, unique column

You can check the table code by clicking the SQL preview button in the top right corner:

You can see your unique key in the SQL code preview

Multicolumn alternate (unique) key

Your unique key may have more than one column. To create a multicolumn one, select the table, expand the Alternate (unique) key section on the right, and click Add key:

To create a multicolumn unique key, select the table, expand the ‘Alternate (unique) key’ section on the right, and then click ‘Add key’

Add all columns you want to include in your key:

Add all columns you want to include in your unique key

Your multicolumn alternate (unique) key is ready (as seen on the SQL code preview):

Your multicolumn alternate (unique) key is ready

Setting an index as unique

You can make an index unique too. Just go to your index:

Expand the properties of the index you want to make unique

Click Set next to the Unique field:

Click ‘Set’ next to the ‘Unique’ field

And set it to Yes:

Make sure that the ‘Unique’ field is set to ‘Yes’

The SQL preview of your unique index looks as follows:

The SQL preview of your unique index

 
 
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