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I would say it's an implementation detail for human readability. Constraint names are optional (in SQL Server at least), but I'd like to have PK_MyTable for MyTable rather than PK_MyTabl___16feb6d8a

I'll answer obliquely... The natural key is always the natural key and should be enforced with a unique constraint or index. This is the "primary key" that flows from your modelling phase. The choic …

BAD PRACTICE ALERT! You need to delimit each string. Not the whole lot. Note where the single quotes are: ("Insert Into dbo.PrnInf(PrnName, PrnSurName, PrnEgn ) Values ('"+txtPrnName.Text+"', …

The order of keys can make a difference depending on your access pattern. Example... You want to find MAX(idPackageVariant) for a singleidHolidayPackage With idHolidayPackage as the second column, …

I'm speculating that the SORT is needed because of parallel plan. I base this on some dim and distant blog article: but I found this on MSDN which may or may not justify this So, try with MAXDOP 1 and …

If we're on about identity or autonumber columns, the value itself should have no meaning. (sometimes it does, as per SO's chat users nentioned by drachenstern, which I've done before myself) However …

The simple version would be to generate a hash from the CLOB and use this as a key. This key will fit into the allowed key width for your engine (900 SQL Server, 767 InnoDB, 1000 MyISAM etc). The has …

One major difference Primary key disallows nullable columns Unique key allows nullable columns Otherwise, there isn't much difference...

I would use my own identifier. The species name may be unique but - it's too long - it's a string For example, in SQL Server, if used as the clustered primary key it will be used in non-clustered i …

"it depends" Yes: Surrogate IDENTITY/AUTONUMBER fields are good when the natural key is wide and non-numeric. Note: this assumes the conflation of "PK" and clustered index that occurs by default in S …

You'd use ALTER TABLE to add the primary key constraint. In Postgres you can "promote" an index using the "ALTER TABLE .. ADD table_constraint_using_index" form Note, the index need to be unique of c …

Yes, on any RDBMS, if you still have a unique index with non-nullable columns to identify individual rows. The difference between a "unique key" and a "primary key" is a PK does not allow NULLs. NULL …

There is no significant disadvantage using the natural key as the clustered index there are no non-clustered indexes no foreign keys referencing this table (it is a parent row) The downside would …

Updates on data already there causes rows to be moved and forward pointers added In this test, we can get 65% fragmentation on 115k densely packed rows CREATE TABLE #FragTest ( FragTestID int NO …

Three things leap out: Your DELETE is on the 2nd column (RespondentID) of the current PK which means a scan, not a seek. Pointless ROWLOCK hint Your "UPSERT" pattern is not concurrency safe. The tes …