Index and or constraint

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Index and or constraint

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Jeff Moden SSC Guru Points: 1004340 More actions · Answer 1

gvoshol 73146 - Thursday, April 6, 2017 5:39 AM
Jeff Moden - Wednesday, April 5, 2017 4:54 PM
I'm thinking that your plan of using MachineID+F1+Kant for the PK //snip//
He can't - 2 of those columns are nullable.
Which also makes a unique constraint harder to implement, but not impossible.

Ah... my apologies. To clarify, I was not suggesting any form of concatenation. It was meant to be a list of columns and I should have just used a comma to separate them.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

GaryV Hall of Fame Points: 3307 More actions · Answer 2

Jeff Moden - Thursday, April 6, 2017 5:10 PM
gvoshol 73146 - Thursday, April 6, 2017 5:39 AM
Jeff Moden - Wednesday, April 5, 2017 4:54 PM
I'm thinking that your plan of using MachineID+F1+Kant for the PK //snip//
He can't - 2 of those columns are nullable.
Which also makes a unique constraint harder to implement, but not impossible.
Ah... my apologies. To clarify, I was not suggesting any form of concatenation. It was meant to be a list of columns and I should have just used a comma to separate them.

But nullable columns are not allowed in a PK, right? Or am I misremembering something?

Jeff Moden SSC Guru Points: 1004340 More actions · Answer 3

gvoshol 73146 - Friday, April 7, 2017 5:13 AM
Jeff Moden - Thursday, April 6, 2017 5:10 PM
gvoshol 73146 - Thursday, April 6, 2017 5:39 AM
Jeff Moden - Wednesday, April 5, 2017 4:54 PM
I'm thinking that your plan of using MachineID+F1+Kant for the PK //snip//
He can't - 2 of those columns are nullable.
Which also makes a unique constraint harder to implement, but not impossible.
Ah... my apologies. To clarify, I was not suggesting any form of concatenation. It was meant to be a list of columns and I should have just used a comma to separate them.
But nullable columns are not allowed in a PK, right? Or am I misremembering something?

Correct but you don't actually need a PK. It can be a UNIQUE clustered or non-clustered index.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)