path: root/sql/item_timefunc.h

/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


/* Function items used by mysql */

#ifdef __GNUC__
#pragma interface			/* gcc class implementation */
#endif

class Item_func_period_add :public Item_int_func
{
public:
  Item_func_period_add(Item *a,Item *b) :Item_int_func(a,b) {}
  longlong val_int();
  const char *func_name() const { return "period_add"; }
  void fix_length_and_dec() 
  { 
    max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
  }
};


class Item_func_period_diff :public Item_int_func
{
public:
  Item_func_period_diff(Item *a,Item *b) :Item_int_func(a,b) {}
  longlong val_int();
  const char *func_name() const { return "period_diff"; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
  }
};


class Item_func_to_days :public Item_int_func
{
public:
  Item_func_to_days(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "to_days"; }
  void fix_length_and_dec() 
  { 
    decimals=0; 
    max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1; 
  }
};


class Item_func_dayofmonth :public Item_int_func
{
public:
  Item_func_dayofmonth(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "dayofmonth"; }
  void fix_length_and_dec() 
  { 
    decimals=0; 
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1; 
  }
};


class Item_func_month :public Item_func
{
public:
  Item_func_month(Item *a) :Item_func(a) {}
  longlong val_int();
  double val() { return (double) Item_func_month::val_int(); }
  String *val_str(String *str) 
  {
    str->set(val_int(), &my_charset_bin);
    return null_value ? 0 : str;
  }
  const char *func_name() const { return "month"; }
  enum Item_result result_type () const { return INT_RESULT; }
  void fix_length_and_dec() 
  { 
    collation.set(&my_charset_bin);
    decimals=0;
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1; 
  }
};


class Item_func_monthname :public Item_func_month
{
public:
  Item_func_monthname(Item *a) :Item_func_month(a) {}
  const char *func_name() const { return "monthname"; }
  String *val_str(String *str);
  enum Item_result result_type () const { return STRING_RESULT; }
  void fix_length_and_dec() 
  {
    collation.set(&my_charset_bin);
    decimals=0;
    max_length=10*my_charset_bin.mbmaxlen;
    maybe_null=1; 
  }
};


class Item_func_dayofyear :public Item_int_func
{
public:
  Item_func_dayofyear(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "dayofyear"; }
  void fix_length_and_dec() 
  { 
    decimals=0;
    max_length=3*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1; 
  }
};


class Item_func_hour :public Item_int_func
{
public:
  Item_func_hour(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "hour"; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};


class Item_func_minute :public Item_int_func
{
public:
  Item_func_minute(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "minute"; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};


class Item_func_quarter :public Item_int_func
{
public:
  Item_func_quarter(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "quarter"; }
  void fix_length_and_dec()
  { 
     decimals=0;
     max_length=1*MY_CHARSET_BIN_MB_MAXLEN;
     maybe_null=1;
  }
};


class Item_func_second :public Item_int_func
{
public:
  Item_func_second(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "second"; }
  void fix_length_and_dec() 
  { 
    decimals=0;
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};


class Item_func_week :public Item_int_func
{
public:
  Item_func_week(Item *a,Item *b) :Item_int_func(a,b) {}
  longlong val_int();
  const char *func_name() const { return "week"; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};

class Item_func_yearweek :public Item_int_func
{
public:
  Item_func_yearweek(Item *a,Item *b) :Item_int_func(a,b) {}
  longlong val_int();
  const char *func_name() const { return "yearweek"; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};


class Item_func_year :public Item_int_func
{
public:
  Item_func_year(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "year"; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=4*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};


class Item_func_weekday :public Item_func
{
  bool odbc_type;
public:
  Item_func_weekday(Item *a,bool type_arg)
    :Item_func(a), odbc_type(type_arg) {}
  longlong val_int();
  double val() { return (double) val_int(); }
  String *val_str(String *str)
  { 
    str->set(val_int(), &my_charset_bin);
    return null_value ? 0 : str;
  }
  const char *func_name() const { return "weekday"; }
  enum Item_result result_type () const { return INT_RESULT; }
  void fix_length_and_dec()
  {
    collation.set(&my_charset_bin);
    decimals=0;
    max_length=1*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1;
  }
};

class Item_func_dayname :public Item_func_weekday
{
 public:
  Item_func_dayname(Item *a) :Item_func_weekday(a,0) {}
  const char *func_name() const { return "dayname"; }
  String *val_str(String *str);
  enum Item_result result_type () const { return STRING_RESULT; }
  void fix_length_and_dec() 
  { 
    collation.set(&my_charset_bin);
    decimals=0; 
    max_length=9*MY_CHARSET_BIN_MB_MAXLEN;
    maybe_null=1; 
  }
};


class Item_func_unix_timestamp :public Item_int_func
{
  String value;
public:
  Item_func_unix_timestamp() :Item_int_func() {}
  Item_func_unix_timestamp(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "unix_timestamp"; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=10*MY_CHARSET_BIN_MB_MAXLEN;
  }
};


class Item_func_time_to_sec :public Item_int_func
{
public:
  Item_func_time_to_sec(Item *item) :Item_int_func(item) {}
  longlong val_int();
  const char *func_name() const { return "time_to_sec"; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=10*MY_CHARSET_BIN_MB_MAXLEN;
  }
};


/* This can't be a Item_str_func, because the val() functions are special */

class Item_date :public Item_func
{
public:
  Item_date() :Item_func() {}
  Item_date(Item *a) :Item_func(a) {}
  enum Item_result result_type () const { return STRING_RESULT; }
  enum_field_types field_type() const { return MYSQL_TYPE_DATE; }
  String *val_str(String *str);
  double val() { return (double) val_int(); }
  const char *func_name() const { return "date"; }
  void fix_length_and_dec()
  { 
    collation.set(&my_charset_bin);
    decimals=0;
    max_length=MAX_DATE_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  int save_in_field(Field *to, bool no_conversions);
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
  }  
};


class Item_date_func :public Item_str_func
{
public:
  Item_date_func() :Item_str_func() {}
  Item_date_func(Item *a) :Item_str_func(a) {}
  Item_date_func(Item *a,Item *b) :Item_str_func(a,b) {}
  enum_field_types field_type() const { return MYSQL_TYPE_DATETIME; }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_datetime(maybe_null, name, t_arg, &my_charset_bin));
  }
};


/* Abstract CURTIME function. Children should define what timezone is used */

class Item_func_curtime :public Item_func
{
  longlong value;
  char buff[9*2+32];
  uint buff_length;
public:
  Item_func_curtime() :Item_func() {}
  Item_func_curtime(Item *a) :Item_func(a) {}
  enum Item_result result_type () const { return STRING_RESULT; }
  enum_field_types field_type() const { return MYSQL_TYPE_TIME; }
  double val() { return (double) value; }
  longlong val_int() { return value; }
  String *val_str(String *str);
  void fix_length_and_dec();
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
  }
  /* 
    Abstract method that defines which time zone is used for conversion.
    Converts time from time_t representation to broken down representation
    in struct tm using gmtime_r or localtime_r functions.
  */
  virtual void store_now_in_tm(time_t now, struct tm *now_tm)=0;
};


class Item_func_curtime_local :public Item_func_curtime
{
public:
  Item_func_curtime_local() :Item_func_curtime() {}
  Item_func_curtime_local(Item *a) :Item_func_curtime(a) {}
  const char *func_name() const { return "curtime"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


class Item_func_curtime_utc :public Item_func_curtime
{
public:
  Item_func_curtime_utc() :Item_func_curtime() {}
  Item_func_curtime_utc(Item *a) :Item_func_curtime(a) {}
  const char *func_name() const { return "utc_time"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


/* Abstract CURDATE function. See also Item_func_curtime. */

class Item_func_curdate :public Item_date
{
  longlong value;
  TIME ltime;
public:
  Item_func_curdate() :Item_date() {}
  void set_result_from_tm(struct tm *now);
  longlong val_int() { return (value) ; }
  void fix_length_and_dec();
  bool get_date(TIME *res, uint fuzzy_date);
  virtual void store_now_in_tm(time_t now, struct tm *now_tm)=0;
};


class Item_func_curdate_local :public Item_func_curdate
{
public:
  Item_func_curdate_local() :Item_func_curdate() {}
  const char *func_name() const { return "curdate"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


class Item_func_curdate_utc :public Item_func_curdate
{
public:
  Item_func_curdate_utc() :Item_func_curdate() {}
  const char *func_name() const { return "utc_date"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


/* Abstract CURRENT_TIMESTAMP function. See also Item_func_curtime */

class Item_func_now :public Item_date_func
{
  longlong value;
  char buff[20*2+32];	// +32 to make my_snprintf_{8bit|ucs2} happy
  uint buff_length;
  TIME ltime;
public:
  Item_func_now() :Item_date_func() {}
  Item_func_now(Item *a) :Item_date_func(a) {}
  enum Item_result result_type () const { return STRING_RESULT; }
  double val()	     { return (double) value; }
  longlong val_int() { return value; }
  int save_in_field(Field *to, bool no_conversions);
  String *val_str(String *str);
  void fix_length_and_dec();
  bool get_date(TIME *res, uint fuzzy_date);
  virtual void store_now_in_tm(time_t now, struct tm *now_tm)=0;
};


class Item_func_now_local :public Item_func_now
{
public:
  Item_func_now_local() :Item_func_now() {}
  Item_func_now_local(Item *a) :Item_func_now(a) {}
  const char *func_name() const { return "now"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


class Item_func_now_utc :public Item_func_now
{
public:
  Item_func_now_utc() :Item_func_now() {}
  Item_func_now_utc(Item *a) :Item_func_now(a) {}
  const char *func_name() const { return "utc_timestamp"; }
  void store_now_in_tm(time_t now, struct tm *now_tm);
};


class Item_func_from_days :public Item_date
{
public:
  Item_func_from_days(Item *a) :Item_date(a) {}
  longlong val_int();
  const char *func_name() const { return "from_days"; }
};


class Item_func_date_format :public Item_str_func
{
  int fixed_length;
  const bool is_time_format;
  String value;
public:
  Item_func_date_format(Item *a,Item *b,bool is_time_format_arg)
    :Item_str_func(a,b),is_time_format(is_time_format_arg) {}
  String *val_str(String *str);
  const char *func_name() const { return "date_format"; }
  void fix_length_and_dec();
  uint format_length(const String *format);
};


class Item_func_from_unixtime :public Item_date_func
{
 public:
  Item_func_from_unixtime(Item *a) :Item_date_func(a) {}
  double val() { return (double) Item_func_from_unixtime::val_int(); }
  longlong val_int();
  String *val_str(String *str);
  const char *func_name() const { return "from_unixtime"; }
  void fix_length_and_dec()
  { 
    collation.set(&my_charset_bin);
    decimals=0;
    max_length=MAX_DATETIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  bool get_date(TIME *res, uint fuzzy_date);
};


class Item_func_sec_to_time :public Item_str_func
{
public:
  Item_func_sec_to_time(Item *item) :Item_str_func(item) {}
  double val() { return (double) Item_func_sec_to_time::val_int(); }
  longlong val_int();
  String *val_str(String *);
  void fix_length_and_dec()
  { 
    collation.set(&my_charset_bin);
    maybe_null=1;
    max_length=MAX_TIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  enum_field_types field_type() const { return MYSQL_TYPE_TIME; }
  const char *func_name() const { return "sec_to_time"; }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
  }
};

/*
  The following must be sorted so that simple intervals comes first.
  (get_interval_value() depends on this)
*/

enum interval_type
{
  INTERVAL_YEAR, INTERVAL_QUARTER, INTERVAL_MONTH, INTERVAL_DAY, INTERVAL_HOUR,
  INTERVAL_MINUTE, INTERVAL_WEEK, INTERVAL_SECOND, INTERVAL_MICROSECOND ,
  INTERVAL_YEAR_MONTH, INTERVAL_DAY_HOUR, INTERVAL_DAY_MINUTE,
  INTERVAL_DAY_SECOND, INTERVAL_HOUR_MINUTE, INTERVAL_HOUR_SECOND,
  INTERVAL_MINUTE_SECOND, INTERVAL_DAY_MICROSECOND, INTERVAL_HOUR_MICROSECOND,
  INTERVAL_MINUTE_MICROSECOND, INTERVAL_SECOND_MICROSECOND
};

class Item_date_add_interval :public Item_date_func
{
  const interval_type int_type;
  String value;
  const bool date_sub_interval;
  enum_field_types cached_field_type;

public:
  Item_date_add_interval(Item *a,Item *b,interval_type type_arg,bool neg_arg)
    :Item_date_func(a,b),int_type(type_arg), date_sub_interval(neg_arg) {}
  String *val_str(String *);
  const char *func_name() const { return "date_add_interval"; }
  void fix_length_and_dec();
  enum_field_types field_type() const { return cached_field_type; }
  double val() { return (double) val_int(); }
  longlong val_int();
  bool get_date(TIME *res, uint fuzzy_date);
  void print(String *str);
};


class Item_extract :public Item_int_func
{
  const interval_type int_type;
  String value;
  bool date_value;
 public:
  Item_extract(interval_type type_arg, Item *a)
    :Item_int_func(a), int_type(type_arg) {}
  longlong val_int();
  const char *func_name() const { return "extract"; }
  void fix_length_and_dec();
  bool eq(const Item *item, bool binary_cmp) const;
  void print(String *str);
};


class Item_typecast :public Item_str_func
{
public:
  Item_typecast(Item *a) :Item_str_func(a) {}
  String *val_str(String *a)
  {
    String *tmp=args[0]->val_str(a);
    null_value=args[0]->null_value;
    if (tmp)
      tmp->set_charset(collation.collation);
    return tmp;
  }
  void fix_length_and_dec()
  {
    collation.set(&my_charset_bin);
    max_length=args[0]->max_length;
  }
  virtual const char* cast_type() const= 0;
  void print(String *str);
};


class Item_char_typecast :public Item_typecast
{
  int cast_length;
  CHARSET_INFO *cast_cs;
  bool charset_conversion;
  String tmp_value;
public:
  Item_char_typecast(Item *a, int length_arg, CHARSET_INFO *cs_arg)
    :Item_typecast(a), cast_length(length_arg), cast_cs(cs_arg) {}
  const char* cast_type() const { return "char"; };
  String *val_str(String *a);
  void fix_length_and_dec();
  void print(String *str);
};


class Item_date_typecast :public Item_typecast
{
public:
  Item_date_typecast(Item *a) :Item_typecast(a) {}
  String *val_str(String *str);
  bool get_date(TIME *ltime, uint fuzzy_date);
  const char *cast_type() const { return "date"; }
  enum_field_types field_type() const { return MYSQL_TYPE_DATE; }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
  }  
};


class Item_time_typecast :public Item_typecast
{
public:
  Item_time_typecast(Item *a) :Item_typecast(a) {}
  String *val_str(String *str);
  bool get_time(TIME *ltime);
  const char *cast_type() const { return "time"; }
  enum_field_types field_type() const { return MYSQL_TYPE_TIME; }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
  }
};


class Item_datetime_typecast :public Item_typecast
{
public:
  Item_datetime_typecast(Item *a) :Item_typecast(a) {}
  String *val_str(String *str);
  const char *cast_type() const { return "datetime"; }
  enum_field_types field_type() const { return MYSQL_TYPE_DATETIME; }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_datetime(maybe_null, name, t_arg, &my_charset_bin));
  }
};

class Item_func_makedate :public Item_str_func
{
public:
  Item_func_makedate(Item *a,Item *b) :Item_str_func(a,b) {}
  String *val_str(String *str);
  const char *func_name() const { return "makedate"; }
  enum_field_types field_type() const { return MYSQL_TYPE_DATE; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=MAX_DATE_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
  }
};


class Item_func_add_time :public Item_str_func
{
  const bool is_date;
  int sign;
  enum_field_types cached_field_type;

public:
  Item_func_add_time(Item *a, Item *b, bool type_arg, bool neg_arg)
    :Item_str_func(a, b), is_date(type_arg) { sign= neg_arg ? -1 : 1; }
  String *val_str(String *str);
  enum_field_types field_type() const { return cached_field_type; }
  void fix_length_and_dec();

/*
  TODO:
       Change this when we support 
       microseconds in TIME/DATETIME
*/
  Field *tmp_table_field(TABLE *t_arg)
  {
    if (cached_field_type == MYSQL_TYPE_TIME)
      return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
    else if (cached_field_type == MYSQL_TYPE_DATETIME)
      return (new Field_datetime(maybe_null, name, t_arg, &my_charset_bin));
    return (new Field_string(max_length, maybe_null, name, t_arg, &my_charset_bin));
  }
  void print(String *str);
};

class Item_func_timediff :public Item_str_func
{
public:
  Item_func_timediff(Item *a, Item *b)
    :Item_str_func(a, b) {}
  String *val_str(String *str);
  const char *func_name() const { return "timediff"; }
  enum_field_types field_type() const { return MYSQL_TYPE_TIME; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=MAX_TIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  Field *tmp_table_field(TABLE *t_arg)
  {
      return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
  }
};

class Item_func_maketime :public Item_str_func
{
public:
  Item_func_maketime(Item *a, Item *b, Item *c)
    :Item_str_func(a, b ,c) {}
  String *val_str(String *str);
  const char *func_name() const { return "maketime"; }
  enum_field_types field_type() const { return MYSQL_TYPE_TIME; }
  void fix_length_and_dec()
  {
    decimals=0;
    max_length=MAX_TIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_time(maybe_null, name, t_arg, &my_charset_bin));
  }
};

class Item_func_microsecond :public Item_int_func
{
public:
  Item_func_microsecond(Item *a) :Item_int_func(a) {}
  longlong val_int();
  const char *func_name() const { return "microsecond"; }
  void fix_length_and_dec() 
  { 
    decimals=0;
    maybe_null=1;
  }
};


class Item_func_timestamp_diff :public Item_int_func
{
  const interval_type int_type;
public:
  Item_func_timestamp_diff(Item *a,Item *b,interval_type type_arg)
    :Item_int_func(a,b), int_type(type_arg) {}
  const char *func_name() const { return "timestamp_diff"; }
  longlong val_int();
  void fix_length_and_dec()
  {
    decimals=0;
    maybe_null=1;
  }
  void print(String *str);
};


enum date_time_format
{
  USA_FORMAT, JIS_FORMAT, ISO_FORMAT, EUR_FORMAT, INTERNAL_FORMAT
};

class Item_func_get_format :public Item_str_func
{
  const timestamp_type type;
public:
  Item_func_get_format(timestamp_type type_arg, Item *a)
    :Item_str_func(a), type(type_arg)
  {}
  String *val_str(String *str);
  const char *func_name() const { return "get_format"; }
  void fix_length_and_dec()
  {
    maybe_null= 1;
    decimals=0;
    max_length=17*MY_CHARSET_BIN_MB_MAXLEN;
  }
  void print(String *str);
};


class Item_func_str_to_date :public Item_date_func
{
public:
  Item_func_str_to_date(Item *a, Item *b)
    :Item_date_func(a, b)
  {}
  String *val_str(String *str);
  bool get_date(TIME *ltime, uint fuzzy_date);
  const char *func_name() const { return "str_to_date"; }
  void fix_length_and_dec()
  {
    maybe_null= 1;
    decimals=0;
    max_length=MAX_DATETIME_FULL_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
};

class Item_func_last_day :public Item_str_func
{
public:
  Item_func_last_day(Item *a) :Item_str_func(a) {}
  String *val_str(String *str);
  const char *func_name() const { return "last_day"; }
  enum_field_types field_type() const { return MYSQL_TYPE_DATE; }
  void fix_length_and_dec()
  { 
    decimals=0;
    max_length=MAX_DATE_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
  }
  Field *tmp_table_field(TABLE *t_arg)
  {
    return (new Field_date(maybe_null, name, t_arg, &my_charset_bin));
  }
};