Section 8.2.1.3, “Index Merge Optimization” 

## index_subquery 

Section 8.8.2, “EXPLAIN Output Format” Section 8.2.2.3, “Optimizing Subqueries with the EXISTS Strategy” 

## R 

[index top] 

## range 

Section 8.2.1.12, “Block Nested-Loop and Batched Key Access Joins” Section 8.8.2, “EXPLAIN Output Format” Section 8.2.1.17, “GROUP BY Optimization” Section 8.2.1.6, “Index Condition Pushdown Optimization” Section 8.2.1.3, “Index Merge Optimization” Section 8.2.1.7, “Nested-Loop Join Algorithms” Section 8.9.3, “Optimizer Hints” Section 8.2.1.2, “Range Optimization” 

## ref 

Section 8.2.1.12, “Block Nested-Loop and Batched Key Access Joins” Section 8.8.2, “EXPLAIN Output Format” Section 8.8.3, “Extended EXPLAIN Output Format” Section 8.2.1.6, “Index Condition Pushdown Optimization” Section 8.3.8, “InnoDB and MyISAM Index Statistics Collection” Section 16.7.1, “MERGE Table Advantages and Disadvantages” NDB Cluster System Variables Section 8.9.3, “Optimizer Hints” Section 8.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions with Merging or Materialization” Section 8.2.2.3, “Optimizing Subqueries with the EXISTS Strategy” 

## ref_or_null 

Section 8.8.2, “EXPLAIN Output Format” Section 8.2.1.6, “Index Condition Pushdown Optimization” Section 8.2.1.15, “IS NULL Optimization” Section 8.2.2.3, “Optimizing Subqueries with the EXISTS Strategy” 

## S 

[index top] 

## system 

Section 8.8.2, “EXPLAIN Output Format” Section 8.8.3, “Extended EXPLAIN Output Format” Section 8.2.1.2, “Range Optimization” Section 13.2.10, “SELECT Statement” 

## U 

[index top] 

