So... I guess you mean something other than a single condition (comparison) that returns a true/false statement.
Perhaps an OR condition?
Never had to use that, but I could imagine that being very useful stuff for data-analysis. At which point speed might not be your first concern, meaning you might as well solve that in code...
It's really hard to reply to a DB question without an actual use-case and data.
Generally, I'd leave logic operations to the language you are developing in.
The rest of the logic should be covered by designing the tables well.
No, I mean something like
JOIN ON a > b
or
JOIN ON a <> b
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