The Backus Naur Form (BNF) is a formal notation to describe programming syntax. The following is the BNF for Query of Queries:
Input ::= select_statement
select_statement ::= select_expression ( <ORDER> <BY> order_by_list )? select_expression ::= ( <OPENPAREN> select_expression <CLOSEPAREN> | select_specification ) ( <UNION> ( <ALL> )? select_expression )? select_specification ::= <SELECT> ( <ALL> | <DISTINCT> )? select_list <FROM> from_table_list ( <WHERE> cond_exp )? ( <GROUP> <BY> group_by_list )? ( <HAVING> cond_exp )? order_by_list ::= order_by_column ( <COMMA> order_by_column )* order_by_column ::= ( <IDENTIFIER> | <INTEGER_LITERAL> ) ( <ASC> | <DESC> )? group_by_list ::= column_ref ( <COMMA> column_ref )* from_table_list ::= <IDENTIFIER> ( <COMMA> <IDENTIFIER> )* select_list ::= select_column ( <COMMA> select_column )* select_column ::= <ASTERISK> | <IDENTIFIER> <DOT> ( <ASTERISK> | <IDENTIFIER> ( alias )? ) | expression ( alias )? alias ::= ( <AS> )? <IDENTIFIER> cond_exp ::= cond_term ( <OR> cond_exp )? cond_term ::= cond_factor ( <AND> cond_term )? cond_factor ::= ( <NOT> )? cond_test cond_test ::= cond_primary ( <IS> ( <NOT> )? ( <TRUE> | <FALSE> | <UNKNOWN> ) )? cond_primary ::= simple_cond | <OPENPAREN> cond_exp <CLOSEPAREN> simple_cond ::= like_cond | null_cond | between_cond | in_cond | comparison_cond null_cond ::= row_constructor <IS> ( <NOT> )? <NULL> comparison_cond ::= row_constructor comparison_operator row_constructor between_cond ::= row_constructor ( <NOT> )? <BETWEEN> row_constructor <AND> row_constructor in_cond ::= row_constructor ( <NOT> )? <IN> <OPENPAREN> ( expression_list ) <CLOSEPAREN> row_constructor ::= expression comparison_operator ::= <LESSEQUAL> | <GREATEREQUAL> | <NOTEQUAL> | <NOTEQUAL2> | <EQUAL> | <LESS> | <GREATER> like_cond ::= string_exp ( <NOT> )? <LIKE> string_exp expression_list ::= expression ( <COMMA> expression )? expression ::= <STRING_LITERAL> | <OPENPAREN> <STRING_LITERAL> <CLOSEPAREN> | numeric_exp numeric_exp ::= numeric_term ( ( <PLUS> | <MINUS> ) numeric_exp )? numeric_term ::= numeric_factor ( ( <ASTERISK> | <SLASH> ) numeric_term )? numeric_factor ::= ( <PLUS> | <MINUS> )? numeric_primary numeric_primary ::= <INTEGER_LITERAL> | <FLOATING_POINT_LITERAL> | aggregate_func | column_ref | <OPENPAREN> numeric_exp <CLOSEPAREN> aggregate_func ::= <COUNT> <OPENPAREN> count_param <CLOSEPAREN> | ( <AVG> | <SUM> | <MIN> | <MAX> ) <OPENPAREN> ( <ALL> | <DISTINCT> )? numeric_exp <CLOSEPAREN> count_param ::= <ASTERISK> | ( <ALL> | <DISTINCT> )? numeric_exp string_exp ::= <STRING_LITERAL> | column_ref | <OPENPAREN> string_exp <CLOSEPAREN> column_ref ::= <IDENTIFIER> ( <DOT> <IDENTIFIER> )?