java - how group by having limit works -

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can explain how construction group + having + limit work? mysql query:

    select         id,         avg(sal)             streamdata              ...     group         id      having         avg(sal)>=10.0          , avg(sal)<=50.0        limit 100

query without limit , having clauses executes 7 seconds, limit - instantly if condition covers large amount of data or ~7 seconds otherwise. documentation says limit executes after having after group by, means query should execute ~7 seconds. please figure out limited limit clause.

using limit 100 tells mysql return first 100 records result set. assuming measuring query time round trip java, 1 component of query time network time needed move result set mysql across network. can take considerable time large result set, , using limit 100 should reduce time 0 or near zero.


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