ADDDATE(ereStart, (SELECT hwyl FROM Stock) * NULLIF(Houmuch, (SELECT SharePrice FROM Stock)) / (SELECT regularPayment FROM Stock)) AS goodThrough

Buried in the middle of the foregoing expression is a NULLIF, because of which the whole thing is NULL if "houmuch" and "SharePrice" are equal. Thus to write it is quite convenient--but if the optimizer is not clever enough, there will be wasted effort in propagating the NULL.

Is the optimizer so clever as to set that test outside the expression, and only then evaluate it when "houmuch" and "SharePrice" are not equal?


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