1710 Optimizing INFORMATION_SCHEMA Queries example, if it is a  MyISAM  table). To obtain the updated distribution statistics, set information_schema_stats_expiry=0 . For  INFORMATION_SCHEMA  tables implemented as views on data dictionary tables, indexes on the underlying data dictionary tables permit the optimizer to construct efficient query execution plans. To see the choices made by the optimizer, use  EXPLAIN . To also see the query used by the server to execute an INFORMATION_SCHEMA  query, use  SHOW WARNINGS  immediately following  EXPLAIN . Consider this statement, which identifies collations for the  utf8mb4  character set: How does the server process that statement? To find out, use  EXPLAIN : To see the query used to statisfy that statement, use  SHOW WARNINGS : mysql>  SHOW WARNINGS\G *************************** 1. row *************************** Level: Note Code: 1003 Message: /* select#1 */ select ‘mysql‘.‘col‘.‘name‘ AS ‘COLLATION_NAME‘ mysql>  EXPLAIN SELECT COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATION_CHARACTER_SET_APPLICABILITY WHERE CHARACTER_SET_NAME = ’utf8mb4’\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: cs partitions: NULL type: const possible_keys: PRIMARY,name key: name key_len: 194 ref: const rows: 1 filtered: 100.00 Extra: Using index *************************** 2. row *************************** id: 1 select_type: SIMPLE table: col partitions: NULL type: ref possible_keys: character_set_id key: character_set_id key_len: 8 ref: const rows: 68 filtered: 100.00 Extra: NULL 2 rows in set, 1 warning (0.01 sec) mysql>  SELECT COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATION_CHARACTER_SET_APPLICABILITY WHERE CHARACTER_SET_NAME = ’utf8mb4’; +----------------------------+ | COLLATION_NAME | +----------------------------+ | utf8mb4_general_ci | | utf8mb4_bin | | utf8mb4_unicode_ci | | utf8mb4_icelandic_ci | | utf8mb4_latvian_ci | | utf8mb4_romanian_ci | | utf8mb4_slovenian_ci | ...