Range query Optimization in sql

by satheeshkumar 2012-09-18 22:02:23

Range query Optimization in sql ,

For a single-part index, index value intervals can be conveniently represented by corresponding conditions in the WHERE clause, so we speak of range conditions rather than “intervals.”

The definition of a range condition for a single-part index is as follows:

For both BTREE and HASH indexes, comparison of a key part with a constant value is a range condition when using the =, <=>, IN(), IS NULL, or IS NOT NULL operators.

Additionally, for BTREE indexes, comparison of a key part with a constant value is a range condition when using the >, <, >=, <=, BETWEEN, !=, or <> operators, or LIKE comparisons if the argument to LIKE is a constant string that does not start with a wildcard character.

For all types of indexes, multiple range conditions combined with OR or AND form a range condition.

“Constant value” in the preceding descriptions means one of the following:

* A constant from the query string

* A column of a const or system table from the same join
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