I have a Table with about 800,000 record
DB Version : 3. 2. 7
The Sql looks like
select x, y, sum(z)/1000 as bw from aa where
a=1 and b=1 and
c =1 and d= 6 group by x, y having count(*) > 1 order by bw desc
limit 10
Column "d" is all set to 6
1/3 of total record is (a=1,b=1,c=1)
1/3 of total record is (a=2,b=2,c=2)
1/3 of total record is (a=3,b=3,c=3)
I just test the above Sql under different index (each time, I just create one
index and drop another)
1) create index 1 on aa (d)
2) create index 2 on aa (a,b,c,d)
Expect :
I think Using second index should be much faster than using first index.
Actually
That two index almost give the same performance. both of them will take
about 15 seconds
Why? thanks in advice :)
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