i can not understand sentences as following:
For a BTREE index, an interval might be usable for conditions combined with
AND, where each condition compares a key part with a constant value using =,
<=>, IS NULL, >, <, >=, <=, !=,<>, BETWEEN, or LIKE 'pattern' (where 'pattern'
does not start with a wildcard). An interval can be used as long as it is
possible to determine a single key tuple containing all records that match the
condition (or two intervals if <> or != is used).
especially the second sentence :
An interval can be used as long as it is possible to determine a single key
tuple containing all records that match the condition (or two intervals if <>
or != is used).
(7.2.5.2. Range Access Method for Multiple-Part Indexes in the manual of mysql)
the example showed in the manual is :
key_part1 = 'foo' AND key_part2 >= 10 AND key_part3 > 10
The single interval is:('foo', 10, 10)< (key_part1, key_part2, key_part3)<
('foo', +inf, +inf)
It is possible that the created interval contains more records than the
initial condition. For example,the preceding interval includes the value
('foo', 11, 0), which does not satisfy the original condition.
thanks
