Hugo Kornelis (4/30/2013)
Sean Lange (4/30/2013)
I don't think I follow you here Tom. The condition checks is @ToCreate = 1. It does not equal 1 because it is NULL. Therefore the boolean check would be false.SQL uses three-valued logic, not true Boolean logic. Any comparison with a NULL (except when using IS [NOT] NULL) will not result in True or False, but in Unknown.
For WHERE and IF, a logic result of True qualifies, and False and Unknown do not qualify.
For CHECK constraints, a logic result of True or Unknown qualifies and False doesn't.
I understand the way NULL is evaluated when doing comparisons.
select * from table where MyNullColumn = MyNonColumn.
I understand that returns NULL.
However for the boolean condition in this question, the TRUE condition is not returned. Therefore it will fall to the else. Maybe I am missing the semantics here. Maybe Tom is just splitting hairs about the verbiage of BOL. Pretty sure we are all on the same page.
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