Geek asks and answers

Is there redundancy when a predicate in an SQL query affects performance?

Consider a query like:

select *
from t
where a = 5 and (a = 5 and b = 7)

Does a redundant predicate affect a = 5query performance. I believe not, but they tell me differently (yes, I know that it depends on the DBMS, but just assume that these are some enterprise DBMSs, such as SQL Server, DB2, or Oracle).

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2 answers

The answer usually will not be, oversupply does not affect performance. Of course, as a programmer, you can use evidence to prove it anyway (unlike a person who will repeat his myths as a fact).

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