You can try this: CREATE UNIQUE CLUSTERED INDEX index_name ON TABLE (col1,col2) or CREATE UNIQUE NONCLUSTERED INDEX index_name ON TABLE (col1,col2) or ALTER TABLE [dbo].[TABLE] ADD CONSTRAINT UNIQUE_Table UNIQUE CLUSTERED ( col1, col2 ) ON [PRIMARY]
This is a misunderstanding. The UNIQUE constraint does exactly what you want. NULL values can coexist in multiple rows in a column defined UNIQUE. The manual: In general, a unique constraint is violated when there is more than one row in the table where the values of all of the columns included in the constraint … Read more
Looks like mysql is case insensitive by default: You probably need to create the column with a case sensitive collation (e.g. utf8_bin): CREATE TABLE WORDS ( ID BIGINT AUTO_INCREMENT, WORD VARCHAR(128) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL UNIQUE, PRIMARY KEY(ID) );
You can’t. The unique_together clause is directly translated to the SQL unique index. And you can only set those on columns of a single table, not a combination of several tables. You can add validation for it yourself though, simply overwrite the validate_unique method and add this validation to it. Docs: http://docs.djangoproject.com/en/dev/ref/models/instances/#django.db.models.Model.validate_unique
You were very close, you can use this: DELETE FROM table WHERE (col1,col2) IN ((1,2),(3,4),(5,6)) Please see this fiddle.
2627 is unique constraint (includes primary key), 2601 is unique index SELECT * FROM sys.messages WHERE text like ‘%duplicate%’ and text like ‘%key%’ and language_id = 1033
How about a LinkedHashSet? Its iterator preserves insertion order, but because it’s a Set, its elements are unique. As its documentation says, Note that insertion order is not affected if an element is re-inserted into the set. In order to efficiently remove elements from the head of this “queue”, go through its iterator: Iterator<?> i … Read more
This happend to me – it turns out you need to resync your primary key fields in Postgres. The key is the SQL statement: SELECT setval(‘tablename_id_seq’, (SELECT MAX(id) FROM tablename)+1);
Some of these approaches seem a little complicated, and I generally do this as: Given table table, want to unique it on (field1, field2) keeping the row with the max field3: DELETE FROM table USING table alias WHERE table.field1 = alias.field1 AND table.field2 = alias.field2 AND table.max_field < alias.max_field For example, I have a table, … Read more
As far as I can tell, there’s no way to do this with Entity Framework at the moment. However, this isn’t just a problem with unique constraints… you may want to create indexes, check constraints, and possibly triggers and other constructs too. Here’s a simple pattern you can use with your code-first setup, though admittedly … Read more