If you have a UNIQUE INDEX then you don’t also need the INDEX – it would be redundant. A UNIQUE INDEX is both a unique constraint and an index that can be used like any other index. From the documentation: Note: The preferred way to add a unique constraint to a table is ALTER TABLE … Read more
Add another column called something like isactive. The create a unique constraint on (username, isactive). Then you can have both an active and inactive user name at the same time. You will not be able to have two active user names. If you want multiple inactive names, use NULL for the value of isactive. NULL … Read more
Add a 4th table specifically for these values you want to be unique then link these keys from this table into the others using a one to many relationship. For example you will have the unique table with an ID, AppName and ItemName to make up its 3 columns. Then have this table link to … Read more
While the following addresses multiple null values, it does not address any “issues” associated with such a design, other than possible database/SQL portability – as such, it should probably not be considered an answer, and is left here merely for reference. This is actually covered in the SQLite FAQ. It is a design choice – … Read more
You can try to make multi-column UNIQUE index with column_1, column_2 and active, and then set active=NULL for the rows where uniqueness not required. Alternatively, you can use triggers (see MySQL trigger syntax) and check for each inserted/updated row if such values are already in the table – but I think it would be rather … Read more
This works as defined by the SQL standard. NULL means unknown. If you have two records of par_cat = NULL and name=”X”, then the two NULLs are not regarded to hold the same value. Thus they don’t violate the unique key constraint. (Well, one could argue that the NULLs still might mean the same value, … Read more
That is something like (for single column constaint): tableName_columnName_key To get constaint name write (in psql): \d tableName or use pg_constraint system catalog: SELECT conname FROM pg_constraint WHERE conrelid = (SELECT oid FROM pg_class WHERE relname LIKE ‘tableName’); Also you can get it from pgAdmin in objects tree.
Create a unique key on those columns ALTER TABLE YourTable add CONSTRAINT YourTable_unique UNIQUE (B, C, D); Oracle/PLSQL: Unique Constraints
You can read liquibase manual also similar problem you can find here In your case it should be: <changeSet author=”liquibase-docs” id=”addUniqueConstraint-example”> <addUniqueConstraint columnNames=”product_id, tournament_id” constraintName=”your_constraint_name” tableName=”person” /> </changeSet>
Solved it thanks to Bear Brown his suggestion. I removed the signal and added UniqueConstraint to the AppVersion model like this: class Meta: db_table=”app_version” constraints = [ models.UniqueConstraint(fields=[‘app_uuid’, ‘version_code’], name=”unique appversion”) ]