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SQL query performance

phman1275
phman1275 asked
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Last Modified: 2019-12-03
I have 3 different but  equivalent queries. Do you mind tell me how to check and see which one has the best execution performance?

-- 1
select a from t1
where mod(a,5) = 0 and b in
( select b from t2
     where c in ( SELECT c FROM t3 where mod(d,5) = 0 ));
     
-- 2
select t1.a from t1, t2, t3 where
t1.b = t2.b and t2.c = t3.c and mod(t1.a,5) = 0 and mod(t3.d,5) = 0;

-- 3
select t1.a from (t1 join t2 on t1.b = t2.b ) join t3 on t2.c = t3.c
where mod(t1.a,5) = 0 and mod(t3.d,5) = 0;
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