/////////////////////////////////////////////////////////////////////////////
//
//  Provider SQL Level 1 Syntax (LL1)
//
//  21-Jun-96       Created        
//  01-Jul-96       Instrinsic functions on constants
//
//  Simple SQL subset for unary queries to be implemented within individual
//  providers.
//
/////////////////////////////////////////////////////////////////////////////

<parse> ::= SELECT <prop_list> FROM <class_name> <opt_where>;

<opt_where> ::= WHERE <expr>;
<opt_where> ::= <>;

<prop_list> ::= <property_name> <prop_list_2>;
<prop_list_2> ::= COMMA <prop_list>;
<prop_list_2> ::= <>;

<property_name> ::= IDENTIFIER;
<property_name> ::= ASTERISK;
<class_name> ::= IDENTIFIER;

// Subexpression nesting.  This particular sequence gives
// a series of AND clauses precedence over OR clauses.

<expr> ::= <term> <expr2>;
<expr2> ::= OR <term> <expr2>;
<expr2> ::= <>;

<term> ::= <simple_expr> <term2>;
<term2> ::= AND <simple_expr> <term2>;
<term2> ::= <>;

// Simple expression types.
// ========================

<simple_expr> ::= NOT <expr>;
<simple_expr> ::= OPEN_PAREN <expr> CLOSE_PAREN;
<simple_expr> ::= IDENTIFIER <leading_ident_expr> <finalize>;
<simple_expr> ::= VARIANT <rel_operator> <trailing_prop_expr> <finalize>;

<trailing_prop_expr> ::=  IDENTIFIER <trailing_prop_expr2>;
<trailing_prop_expr2> ::= OPEN_PAREN IDENTIFIER CLOSE_PAREN;
<trailing_prop_expr2> ::= <>;

<leading_ident_expr> ::= OPEN_PAREN <unknown_func_expr>;
<leading_ident_expr> ::= <comp_operator> <trailing_const_expr>;
<leading_ident_expr> ::= <equiv_operator> <trailing_or_null>;
<leading_ident_expr> ::= <is_operator> NULL;

<unknown_func_expr> ::= IDENTIFIER CLOSE_PAREN <rel_operator> <trailing_const_expr>;
<unknown_func_expr> ::= <typed_constant> CLOSE_PAREN <rel_operator> <trailing_prop_expr>;

<trailing_or_null> ::= NULL;
<trailing_or_null> ::= <trailing_const_expr>;
<trailing_or_null> ::= <trailing_prop_expr>;

<trailing_const_expr> ::= <typed_constant>;
<trailing_const_expr> ::= IDENTIFIER OPEN_PAREN <typed_constant> CLOSE_PAREN;

<typed_constant> ::= VARIANT; // VT_R8, VT_I4, VT_BSTR

<finalize> ::= <>; 
    // This is just a semantic production in the parser to allow
    // all the important code to be located in one place.

<rel_operator> ::= <equiv_operator>;
<rel_operator> ::= <comp_operator>;

<equiv_operator> ::= EQUIVALENT_OPERATOR; // =, !=
<comp_operator> ::=  COMPARE_OPERATOR;  // <=, >=, <, >, like
<is_operator> ::=  ISNOT_OPERATOR;  // IS, IS NOT