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Null values in primary key

Null values in primary key

(OP)
Is it true that null values is not allowed in primary keys in Mimer?

RE: Null values in primary key

Null values are not allowed in primary keys. This is actually a SQL92 feature.

If you want a key that allows NULL values you can use UNIQUE (in create table). Note, however, that NULL values are not considered equal so multiple rows with null values in the same column are allowed (SQL standard again!).

Finally, you can create a UNIQUE index. In this case null values are treated as equal, so the table cannot have multiple rows with null values in the same column.

Pick the constraint of your choice!

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