scalar-expression ::= 
     term {scalar-operator term}

scalar-operator ::= 
     + | - | * | / | \ | # | "||"

term ::= 
     literal | 
     CURRENT_DATE  |
     scalar function | 
     agg |
     unary | 
     column | 
     host-variable | 
     extended function |
     NULL | 
     case | 
     odbc escape | 
     scalar-expression

scalar function ::=  
     ABS |
     CAST |
		CHAR_LENGTH |
     CHARACTER_LENGTH | 
     CURRENT_TIME |
     CURRENT_TIMESTAMP | 
		DECODE |
     ISNULL | 
     LOWER |
     NVL |
     POSITION | 
     SIGN | 
     SUBSTR |
     SUBSTRING |
     TODATE | 
     TONUMBER |
     TRIM