Optimizer Hints •  GROUP_INDEX ,  NO_GROUP_INDEX : Enable or disable the specified index or indexes for index scans for  GROUP BY  operations. Equivalent to the index hints  FORCE INDEX FOR GROUP BY ,  IGNORE INDEX FOR GROUP BY . Available in MySQL 8.0.20 and later. •  INDEX ,  NO_INDEX : Acts as the combination of  JOIN_INDEX ,  GROUP_INDEX , and  ORDER_INDEX , forcing the server to use the specified index or indexes for any and all scopes, or as the combination of  NO_JOIN_INDEX ,  NO_GROUP_INDEX , and  NO_ORDER_INDEX , which causes the server to ignore the specified index or indexes for any and all scopes. Equivalent to  FORCE INDEX ,  IGNORE INDEX . Available beginning with MySQL 8.0.20. •  INDEX_MERGE ,  NO_INDEX_MERGE : Enable or disable the Index Merge access method for the specified table or indexes. For information about this access method, see Section 8.2.1.3, “Index Merge Optimization” . These hints apply to all three Index Merge algorithms. •  JOIN_INDEX ,  NO_JOIN_INDEX : Forces MySQL to use or ignore the specified index or indexes for any access method, such as  ref ,  range ,  index_merge , and so on. Equivalent to  FORCE INDEX FOR JOIN ,  IGNORE INDEX FOR JOIN . Available in MySQL 8.0.20 and later. •  MRR ,  NO_MRR : Enable or disable MRR for the specified table or indexes. MRR hints apply only to InnoDB  and  MyISAM  tables. For information about this access method, see Section 8.2.1.11, “Multi- Range Read Optimization” . •  NO_ICP : Disable ICP for the specified table or indexes. By default, ICP is a candidate optimization strategy, so there is no hint for enabling it. For information about this access method, see Section 8.2.1.6, “Index Condition Pushdown Optimization” . •  NO_RANGE_OPTIMIZATION : Disable index range access for the specified table or indexes. This hint also disables Index Merge and Loose Index Scan for the table or indexes. By default, range access is a candidate optimization strategy, so there is no hint for enabling it. •  ORDER_INDEX ,  NO_ORDER_INDEX : Cause MySQL to use or to ignore the specified index or indexes for sorting rows. Equivalent to  FORCE INDEX FOR ORDER BY ,  IGNORE INDEX FOR ORDER BY . Available beginning with MySQL 8.0.20. •  SKIP_SCAN ,  NO_SKIP_SCAN : Enable or disable the Skip Scan access method for the specified table or indexes. For information about this access method, see Skip Scan Range Access Method. These hints are available as of MySQL 8.0.13. 1799 This hint may be useful when the number of ranges may be high and range optimization would require many resources. The  SKIP_SCAN  hint forces the optimizer to use Skip Scan for the specified table using the specified set of indexes. If no index is specified, the optimizer considers all possible indexes and selects the least expensive one. The hint may be ignored if the index is inapplicable to the given statement. The  NO_SKIP_SCAN  hint disables Skip Scan for the specified indexes. If the hint specifies no indexes, Skip Scan is not permitted for the table. The  INDEX_MERGE  hint forces the optimizer to use Index Merge for the specified table using the specified set of indexes. If no index is specified, the optimizer considers all possible index combinations and selects the least expensive one. The hint may be ignored if the index combination is inapplicable to the given statement. The  NO_INDEX_MERGE  hint disables Index Merge combinations that involve any of the specified indexes. If the hint specifies no indexes, Index Merge is not permitted for the table.