function_ref:
          aggregate_fcn | scalar_fcn

aggregate_fcn:
          calc_fcn_name ( [DISTINCT] arith_expr ) 
     |    COUNT{* | column_var })
     |    {EVERY | ANY | SOME} ( conditional_expr )
     |    {MIN | MAX | INVAR} (value_expr)
     |    agg_udf_name( [DISTINCT] value_expr)

calc_fcn_name:
          SUM | AVG | VAR_SAMP | VAR_POP | STDDEV_SAMP | STDDEV_POP

scalar_fcn:
          IF (conditional_expr, value_expr1, value_expr2)
     |    numeric_function | datetime_function | string_function | misc_function
     |    scalar_udf_name (value_expr1[, value_expr2]...)

numeric_function:
          abs(arith_expr)
     |    acos(arith_expr)
     |    asin(arith_expr)
     |    atan(arith_expr)
     |    atan2(arith_expr1, arith_expr2)
     |    {ceil | ceiling}(arith_expr)
     |    cos(arith_expr)
     |    cot(arith_expr)
     |    degrees(arith_expr)
     |    exp(arith_expr)
     |    floor(arith_expr)
     |    {ln | log}(arith_expr)
     |    mod(arith_expr1, arith_expr2)
     |    pi()
     |    power(arith_expr1, arith_expr2)
     |    rand(num)
     |    round(arith_expr)
     |    sign(arith_expr)
     |    sin(arith_expr)
     |    sqrt(arith_expr)
     |    tan(arith_expr)

datetime_function:
          age(dt_expr)
     |    {curdate | current_date}()
     |    {curtime | current_time}()
     |    {curts | current_timestamp}()
     |    dayofmonth(dt_expr)
     |    dayofweek(dt_expr)
     |    dayofyear(dt_expr)
     |    hour(dt_expr)
     |    minute(dt_expr)
     |    month(dt_expr)
     |    quarter(dt_expr)
     |    second(dt_expr)
     |    trunctime (dt_expr, tt_spec)
     |    week(dt_expr)
     |    year(dt_expr)

string_function:
          ascii(string_expr)
     |    CHAR(num)
     |    {char_length | character_length}(string_expr)
     |    CONCAT(left_string_expr, right_string_expr)
     |    CONVERT(value_expr, {convert_type | {  | WCHAR}, width_num, convert_format})
     |    insstr(target_string_expr, offset_num, count_num, replacement_string_expr)
     |    lcase(string_expr)
     |    left(string_expr, count_num)
     |    length(string_expr)
     |    locate(match_string_expr, search_string_expr, startpos_num)
     |    ltrim(string_expr)
     |    octet_length(string_expr)
     |    position(match_string_expr, search_string_expr)
     |    repeat(string_expr, count_num)
     |    replace(string_expr, string_expr, string_expr)
     |    right(string_expr, count_num)
     |    rtrim(string_expr)
     |    substring(string_expr, startpos_num, length_num)
     |    trim(num, string_expr, string_expr)
     |    ucase(string_expr)
     |    unicode(string_expr)
     |    WCHAR(num)

misc_function:
          DATABASE()
     |    COALESCE(value_expr1, value_expr2, value_exprN)
     |    ROWNUMBER()
     |    IFNULL(value_expr1, value_expr2)
     |    TYPEOF(value_expr)

tt_spec:
          "1S" | "5S" | "10S" | "15S" | "20S" | "30S" | "1M"  | "5M" 
     |    "10M" | "15M" | "20M" | "30M" | "1H" | "3H" | "4H" 
     |    "6H" | "8H" | "12H"

convert_type:
          CHAR | TINYINT | SMALLINT | INTEGER | BIGINT | REAL | DATE | TIME | TIMESTAMP

convert_format:
          numeric_format | datetime_format

numeric_format:
          "[<< | >> | ><]['text' | $][- | (][#,]#[.#[#]...][e | E]['text' | $ | %]"

datetime_format:
          "[<< | >> | ><]['text' | spchar | date_code | time_code]..."

date_code:
          m | mm | mmm | mon | mmmm | month
     |    d | dd | ddd | dddd | day
     |    yy | yyyy

time_code:
          h | hh | m | mm | s | ss | .f[f]... | [a/p | am/pm | A/P | AM/PM]