query:	SET OPTIMIZER_USE_MRR = 'DISABLE' |
	EXPLAIN select | EXPLAIN select |
	EXPLAIN select | EXPLAIN select |
	select | select |
	select | select ;

select: 
	SELECT outer_select_item
	FROM outer_from
	WHERE subquery_expression logical_operator outer_condition_top
	outer_group_by outer_having limit;

outer_select_item:
	OUTR . field_name AS X |
	aggregate_function OUTR . field_name ) AS X;

aggregate_function:
	AVG( |
	BIT_AND( | BIT_OR( | BIT_XOR( |
	COUNT(DISTINCT | COUNT( |
	GROUP_CONCAT( |
	MIN( | MIN(DISTINCT |
	MAX( | MAX(DISTINCT |
	STD( | STDDEV_POP( | STDDEV_SAMP( |
	SUM( | SUM(DISTINCT |
	VAR_POP( | VAR_SAMP( | VARIANCE( ;

aggregate_function_disabled:
 AVG(DISTINCT ;

outer_from:
	outer_table_name AS OUTR |
	outer_table_name AS OUTR2 LEFT JOIN outer_table_name AS OUTR ON ( OUTR2 . field_name arithmetic_operator OUTR . field_name );

outer_group_by:
	| GROUP BY OUTR . field_name |
	GROUP BY OUTR . field_name WITH ROLLUP;

outer_having:
	| HAVING X arithmetic_operator value ;

limit:
	| LIMIT digit ;

select_inner:
	SELECT inner_select_item
	FROM inner_from
	WHERE inner_condition_top
	inner_group_by inner_having;

select_inner_two_cols:
	SELECT INNR . field_name AS X , INNR . field_name AS Z 
	FROM inner_from
	WHERE inner_condition_top
	inner_group_by inner_having;

inner_group_by:
	;
inner_group_by_disabled:
	| GROUP BY INNR . field_name |
	GROUP BY INNR . field_name WITH ROLLUP;

inner_having:
	| HAVING X arithmetic_operator value ;

inner_select_item:
	INNR . field_name AS Y |
	aggregate_function INNR . field_name ) AS Y ;


inner_from:
	inner_table_name AS INNR |
	inner_table_name AS INNR2 LEFT JOIN inner_table_name AS INNR ON ( INNR2 . field_name arithmetic_operator INNR . field_name );

select_inner_one_row:
	select_inner LIMIT 1;

outer_condition_top:
	outer_condition_bottom |
	( outer_condition_bottom logical_operator outer_condition_bottom ) |
	outer_condition_bottom logical_operator outer_condition_bottom ;

outer_condition_bottom:
	OUTR . field_name null_operator |
	OUTR . field_name arithmetic_operator value |
	OUTR . field_name arithmetic_operator OUTR . field_name;

inner_condition_top:
	inner_condition_bottom |
	outer_condition_bottom |
	inner_condition_bottom logical_operator inner_condition_bottom |
	inner_condition_bottom logical_operator outer_condition_bottom ;

inner_condition_bottom:
	INNR . field_name null_operator |
	INNR . field_name arithmetic_operator value |
	INNR . field_name arithmetic_operator INNR . field_name;
	INNR . field_name arithmetic_operator OUTR . field_name;

null_operator: IS NULL | IS NOT NULL ;
logical_operator: AND | OR | AND NOT ;
arithmetic_operator: = | > | < | <> | >= | <= ;

subquery_expression:
	EXISTS ( select_inner ) |
	NOT EXISTS ( select_inner ) |
	OUTR . field_name IN ( select_inner ) |
	( OUTR . field_name , OUTR . field_name ) IN ( select_inner_two_cols ) |
	OUTR . field_name NOT IN ( select_inner ) |
	( OUTR . field_name , OUTR . field_name ) NOT IN ( select_inner_two_cols ) |
	OUTR . field_name arithmetic_operator ( select_inner_one_row ) |
	OUTR . field_name arithmetic_operator subquery_word ( select_inner ) ;

subquery_word: SOME | ANY | ALL ;

field_name:
	`pk` | `int_key` | `int_nokey` |
	`date_key` | `date_nokey` |
	`time_key` | `time_nokey` |
	`datetime_key` | `datetime_nokey` ;

outer_table_name:
	A | B | C ;

inner_table_name:
	AA | BB | CC ;

value: tinyint_unsigned | date | time | datetime ;