Ehhh, I don’t quite agree with this. I’ve done the same thing where I used a timestamp field to replace a boolean. However, they are technically not the same thing. In databases, boolean fields can be nullable so you actually have 3-valued boolean logic:
true
,false
, andnull
. You can technically only replace a non-nullable field to a timestamp column because you are treatingnull
in timestamp asfalse
.Two examples:
-
A table of generated documents for employees to sign. There’s a field where they need to agree to something, but it’s optional. You want to differentiate between employees who agreed, employees who disagreed, and employees who have yet to agree. You can’t change the column from
is_agreed
toagreed_at
. -
Adding a boolean column to an existing table. These columns need to either default to an value (which is fair) or be nullable.
Yeah, this feels like “premature optimization”. When you design your applications and databases, it should reflect your understanding of the problem and how you solved it as best as possible. Using
DATETIMEOFFSET NULL
when you actually meanBIT NOT NULL
isn’t saying what you mean. If you already understand that you have a boolean option and you think you might need a timestamp to track it, use 2 columns. Or an audit table. So sayeth the holy SRP.
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