SQL Server bit column constraint, 1 row = 1, all others 0

Question

I have a bit IsDefault column. Only one row of data within the table may have this bit column set to 1, all the others must be 0.

Answer 1

All versions:

• Trigger
• Indexed view
• Stored proc (eg test on write)

SQL Server 2008: a filtered index

CREATE UNIQUE INDEX IX_foo ON bar (MyBitCol) WHERE MyBitCol = 1