The manual says that if two seprate single-column
indexes exist on two different colums (col1, col2)
and someone issues a query:
SELECT * FROM tbl_name WHERE col1=val1 AND col2=val2
optimizer will choose the index which matches the least
records and use it.
This is it. Manual does not say what happens nexts.
Assuming exactly what has been said abouve we have
a terrible situation. For example if tbl_name has
100,000 records in col1 and for each of the
values we have 100,000 values in col2.
In this case MySQL would have too look through
thousands of records to get the results if it does not
apply another index after using the first one.
So, my question is: Are things so bad? MySQL cannot
apply more than one index per query per table?
Regards,
Artem
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