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sqlsql-servercheck-constraints

Create Unique Check + Additional Check in MS SQL Constraint

I need to add a constraint to the following table:

Table(
CategoryId INT,
CustomerId INT,
IsActive BIT
....
)

I want to have only one combination of (CategoryId, CustomerId, IsActive = 1) just have no idea how to put that in one constraint. Only one combination of Category and Customer to be active (Active = 1) at the time, and be able to have multiple with active = 0

I know it can be done with function, but I'm trying to find a way without it. Something like:

CONSTRAINT UN_CK_Table UNIQUE(CategoryId, CustomerId, IsActive = 1)

Solution

  • You can use a filtered unique index:

    CREATE UNIQUE INDEX YourTableUi1 ON YourTable (CategoryId, CustomerId) WHERE (IsActive = 1);