programming

Agile Web Development in Rails 4

Book Notes

Okay, I read this one again, since the first reading was before I knew what things were and why I was doing things and oh, god, what have I gotten myself into? Helps to have development under your belt for these things.

This book was recommended to me as the book to learn Rails development. It has two main sections: a hands-on let's-build-a-rails-app section, and a here-are-the-explanations section. The first is designed to guide you through building an application with Rails, the second to explain what the hell just happened and how all the parts fit together. The book builds a slight e-commerce platform: a store's product display / catalog, administration section, shopping cart, checkout and user authentication. The example is great, I definitely liked that it wasn't a blog or a twitter client.

The book is good and it works. It is not the book for new developers, however. It uses a lot of words and concepts without explaining them, assuming the reader knows what they mean. And this is okay. The book is for a developer who is learning Rails. It does that well.

Time-wise, if you're going to read the book and do the exercises (say, a new employer is giving you a chance to come up to speed with Rails, or the first couple weeks of work to learn), give yourself 2 work weeks to go through it. You can do it faster (you can always do things faster), but doing the exercises and typing things in and playing around with things relevant-to but not part-of the lessons is what makes learning better. So, yeah, play around, poke around, learn something outside the lesson for greater good.

Recursion

Blog

I made some comment to Kris recently about how I wish I had more formal computer science training. I took all of two programming classes in college, and learned the rest on my own. I believe I do okay, since programming is essentially solving one big logic problem, but every so often I solve a problem with brute force instead of creating an elegant solution.

Kris offered to help me out with the formal computer science education, and suggested we go through his Algorithms book. I agreed, figuring it would happen not before next year, given all of my copious free time.

When I was at Hackday yesterday, Kris pinged me and asked if PHP could handle recursion, which cracked me up (the answer being, uh, yes, of course). When I said yes, he asked me if I could write a recursive function that printed out a series of numbers, from one to the single function argument N. The two keys to this problem were recursion and single parameter.

Counting down from N to 1 was easy. I figure both are easy, but counting down is clearly the easier:

function kris($n = 1) {
  print "$n ";
  if ($n > 1) {
    kris($n - 1);
  }
}

Oddly enough, counting up was harder for me. I told Kris he couldn't offer any hints, and eventually I figured out a convoluted solution using a static variable. My solution clearly showed me my lack of CS education. Kris' solution was much simpler:

function kitt($n=1) { 
  if ($n>1) { 
    kitt($n-1);
  }
  print "$n ";
}

As Kris commented, people forget you can do the recursion first, and the action second, when writing recursive functions.

A candidate at Kris' work was unable to solve the problem, and he wanted to see if I could, especially since I was commenting on the CS education I didn't have. I did solve it, but not correctly.

Next time, I'll have the trick. This time? I felt like an idiot.

How to keep an SSH tunnel open in MacOS X

Guest Post Blog
Kitt asked me to post this, so here goes: ssh_command_no_exit.sh as follows:
ssh -N -l remoteprocess -L13307:127.0.0.1:3306 -R13307:127.0.0.1:3306 -o ServerAliveInterval=240 re.mo.te.ip
/Library/LaunchDaemons/ssh_tunneler.plist as follows:




   Label
   ssh_tunneler
   ProgramArguments
   
      /path/to/ssh_command_no_exit.sh
   
   OnDemand
   
   Disabled
   


This basically sets up the equivalent of an inittab:respawn on Linux. OnDemand=false indicates that the server should be continuously running. Type in
launchctl load /Library/LaunchDaemons/ssh_tunneler.plist
Finally, launchd kills something that fails within 60 seconds 10 times in a row. If our DSL/cable line goes out, this could take longer. So, add the following line to crontab:
#Re-list the ssh_tunneler
10      0       *       *       0       launchd load /Library/LaunchDaemons/ssh_tunnelr.plist >> /dev/null &2>1

Using Bharat's Time Turner

Blog

Much to my pleasure, I have finally found a project that interests me enough to begin using Bharat's Time Turner with it. I've installed a development environment on my laptop that means every time I have two minutes to work on it, zing! out comes the laptop, and I start working.

Because everyone knows I don't go anywhere without my laptop.

Gah! Two minutes wasted typing this up!

Note to self re: barcode scanners

Blog

I'm sure to forget this, so I'll write it down here, for when I implement the roster barcode scanner part of the rostering system for college. Via Joel on Software's article on How to Ship Anything:

"I didn't really know which barcode scanner to buy, and no matter how hard I tried, I couldn't find any online reviews of barcode scanners. I did find out that the kind of scanner I wanted was a USB keyboard wedge scanner. That means that it has a USB port, which makes connection simple, and it behaves exactly like a keyboard as far as your computer is concerned. I also found out that I wanted a laser scanner, not a CCD scanner, because it works at a distance. I ended up buying a Wasp WSL-9000 along with the stand which you can see in the picture. So far it's been great.

Setting up the barcode reader was the easiest thing in the world. Plug it in to a USB port, and you're done. It comes with a whole book of barcodes that you can scan to configure it to behave in many interesting ways, which you can throw away. Without any setup, when you scan a barcode, your scanner will type the letters that barcode represents on the keyboard and press Enter."

According to Google, though, that's the only place on the web that refers to that scanner as "Wasp WSL-9000", so search for Wasp WSL 9000" (no dash).

And get the one with the USB cable.

MySQL date / time functions

Book page

From: http://mysqld.active-venture.com/Date_and_time_functions.html

MySQL Open Source Database - Date and Time Functions
  

Date and Time Functions

This section describes the functions that can be used to manipulate temporal values. See section 6.2.2 Date and Time Types for a description of the range of values each date and time type has and the valid formats in which values may be specified.

Here is an example that uses date functions. The following query selects all records with a date_col value from within the last 30 days:

mysql> SELECT something FROM tbl_name
           WHERE TO_DAYS(NOW()) - TO_DAYS(date_col) <= 30;

(Note that the query will also select records with dates that lie in the future.)

Functions that expect date values usually will accept datetime values and ignore the time part. Functions that expect time values usually will accept datetime values and ignore the date part.

Functions that return the current date or time each are evaluated only once per query at the start of query execution. This means that multiple references to a function such as NOW() within a single query will always produce the same result. This principle also applies to CURDATE(), CURTIME(), UTC_DATE(), UTC_TIME(), UTC_TIMESTAMP(), and any of their synonyms.

The return value ranges in the following function descriptions apply for complete dates. If a date is a ``zero'' value or an incomplete date such as '2001-11-00', functions that extract a part of a date may return 0. For example, DAYOFMONTH('2001-11-00') returns 0.

ADDDATE(date,INTERVAL expr type)
 
ADDDATE(expr,days)
When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB().
mysql> SELECT DATE_ADD('1998-01-02', INTERVAL 31 DAY);
        -> '1998-02-02'
mysql> SELECT ADDDATE('1998-01-02', INTERVAL 31 DAY);
        -> '1998-02-02'
As of MySQL 4.1.1, the second syntax is allowed, where expr is a date or datetime expression and days is the number of days to be added to expr.
mysql> SELECT ADDDATE('1998-01-02', 31);
        -> '1998-02-02'
ADDTIME(expr,expr2)
ADDTIME() adds expr2 to expr and returns the result. expr is a date or datetime expression, and expr2 is a time expression.
mysql> SELECT ADDTIME("1997-12-31 23:59:59.999999", "1 1:1:1.000002");
        -> '1998-01-02 01:01:01.000001'
mysql> SELECT ADDTIME("01:00:00.999999", "02:00:00.999998");
        -> '03:00:01.999997'
ADDTIME() was added in MySQL 4.1.1. 
CURDATE()
Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context:
mysql> SELECT CURDATE();
        -> '1997-12-15'
mysql> SELECT CURDATE() + 0;
        -> 19971215
CURRENT_DATE
 
CURRENT_DATE()
CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE()
CURTIME()
Returns the current time as a value in 'HH:MM:SS' or HHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT CURTIME();
        -> '23:50:26'
mysql> SELECT CURTIME() + 0;
        -> 235026
CURRENT_TIME
 
CURRENT_TIME()
CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME()
CURRENT_TIMESTAMP
 
CURRENT_TIMESTAMP()
CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW()
DATE(expr)
Extracts the date part of the date or datetime expression expr.
mysql> SELECT DATE('2003-12-31 01:02:03');
        -> '2003-12-31'
DATE() is available as of MySQL 4.1.1. 
DATEDIFF(expr,expr2)
DATEDIFF() returns the number of days between the start date expr and the end date expr2. expr and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.
mysql> SELECT DATEDIFF('1997-12-31 23:59:59','1997-12-30');
        -> 1
mysql> SELECT DATEDIFF('1997-11-31 23:59:59','1997-12-31');
        -> -30
DATEDIFF() was added in MySQL 4.1.1. 
DATE_ADD(date,INTERVAL expr type)
 
DATE_SUB(date,INTERVAL expr type)
These functions perform date arithmetic. As of MySQL Version 3.23, INTERVAL expr type is allowed on either side of the + operator if the expression on the other side is a date or datetime value. For the - operator, INTERVAL expr type is allowed only on the right side, because it makes no sense to subtract a date or datetime value from an interval. (See examples below.) date is a DATETIME or DATE value specifying the starting date. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a `-' for negative intervals. type is a keyword indicating how the expression should be interpreted. The following table shows how the type and expr arguments are related:
type Value Expected expr Format
SECOND SECONDS
MINUTE MINUTES
HOUR HOURS
DAY DAYS
MONTH MONTHS
YEAR YEARS
MINUTE_SECOND 'MINUTES:SECONDS'
HOUR_MINUTE 'HOURS:MINUTES'
DAY_HOUR 'DAYS HOURS'
YEAR_MONTH 'YEARS-MONTHS'
HOUR_SECOND 'HOURS:MINUTES:SECONDS'
DAY_MINUTE 'DAYS HOURS:MINUTES'
DAY_SECOND 'DAYS HOURS:MINUTES:SECONDS'
DAY_MICROSECOND 'DAYS.MICROSECONDS'
HOUR_MICROSECOND 'HOURS.MICROSECONDS'
MINUTE_MICROSECOND 'MINUTES.MICROSECONDS'
SECOND_MICROSECOND 'SECONDS.MICROSECONDS'
MICROSECOND 'MICROSECONDS'
The type values DAY_MICROSECOND, HOUR_MICROSECOND, MINUTE_MICROSECOND, SECOND_MICROSECOND, and MICROSECOND are allowed as of MySQL 4.1.1. MySQL allows any punctuation delimiter in the expr format. Those shown in the table are the suggested delimiters. If the date argument is a DATE value and your calculations involve only YEAR, MONTH, and DAY parts (that is, no time parts), the result is a DATE value. Otherwise, the result is a DATETIME value:
mysql> SELECT '1997-12-31 23:59:59' + INTERVAL 1 SECOND;
        -> '1998-01-01 00:00:00'
mysql> SELECT INTERVAL 1 DAY + '1997-12-31';
        -> '1998-01-01'
mysql> SELECT '1998-01-01' - INTERVAL 1 SECOND;
        -> '1997-12-31 23:59:59'
mysql> SELECT DATE_ADD('1997-12-31 23:59:59',
    ->                 INTERVAL 1 SECOND);
        -> '1998-01-01 00:00:00'
mysql> SELECT DATE_ADD('1997-12-31 23:59:59',
    ->                 INTERVAL 1 DAY);
        -> '1998-01-01 23:59:59'
mysql> SELECT DATE_ADD('1997-12-31 23:59:59',
    ->                 INTERVAL '1:1' MINUTE_SECOND);
        -> '1998-01-01 00:01:00'
mysql> SELECT DATE_SUB('1998-01-01 00:00:00',
    ->                 INTERVAL '1 1:1:1' DAY_SECOND);
        -> '1997-12-30 22:58:59'
mysql> SELECT DATE_ADD('1998-01-01 00:00:00',
    ->                 INTERVAL '-1 10' DAY_HOUR);
        -> '1997-12-30 14:00:00'
mysql> SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
        -> '1997-12-02'
mysql> SELECT DATE_ADD('1992-12-31 23:59:59.000002',
    ->                 INTERVAL '1.999999' SECOND_MICROSECOND);
        -> '1993-01-01 00:00:01.000001'
If you specify an interval value that is too short (does not include all the interval parts that would be expected from the type keyword), MySQL assumes you have left out the leftmost parts of the interval value. For example, if you specify a type of DAY_SECOND, the value of expr is expected to have days, hours, minutes, and seconds parts. If you specify a value like '1:10', MySQL assumes that the days and hours parts are missing and the value represents minutes and seconds. In other words, '1:10' DAY_SECOND is interpreted in such a way that it is equivalent to '1:10' MINUTE_SECOND. This is analogous to the way that MySQL interprets TIME values as representing elapsed time rather than as time of day. Note that if you add to or subtract from a date value something that contains a time part, the result is automatically converted to a datetime value:
mysql> SELECT DATE_ADD('1999-01-01', INTERVAL 1 DAY);
        -> '1999-01-02'
mysql> SELECT DATE_ADD('1999-01-01', INTERVAL 1 HOUR);
        -> '1999-01-01 01:00:00'
If you use really malformed dates, the result is NULL. If you add MONTH, YEAR_MONTH, or YEAR and the resulting date has a day that is larger than the maximum day for the new month, the day is adjusted to the maximum days in the new month:
mysql> SELECT DATE_ADD('1998-01-30', interval 1 month);
        -> '1998-02-28'
Note from the preceding example that the keyword INTERVAL and the type specifier are not case-sensitive. 
DATE_FORMAT(date,format)
Formats the date value according to the format string. The following specifiers may be used in the format string:
Specifier Description
%M Month name (January..December)
%W Weekday name (Sunday..Saturday)
%D Day of the month with English suffix (0th, 1st, 2nd, 3rd, etc.)
%Y Year, numeric, 4 digits
%y Year, numeric, 2 digits
%X Year for the week where Sunday is the first day of the week, numeric, 4 digits; used with %V
%x Year for the week, where Monday is the first day of the week, numeric, 4 digits; used with %v
%a Abbreviated weekday name (Sun..Sat)
%d Day of the month, numeric (00..31)
%e Day of the month, numeric (0..31)
%m Month, numeric (00..12)
%c Month, numeric (0..12)
%b Abbreviated month name (Jan..Dec)
%j Day of year (001..366)
%H Hour (00..23)
%k Hour (0..23)
%h Hour (01..12)
%I Hour (01..12)
%l Hour (1..12)
%i Minutes, numeric (00..59)
%r Time, 12-hour (hh:mm:ss followed by AM or PM)
%T Time, 24-hour (hh:mm:ss)
%S Seconds (00..59)
%s Seconds (00..59)
%f Microseconds (000000..999999)
%p AM or PM
%w Day of the week (0=Sunday..6=Saturday)
%U Week (00..53), where Sunday is the first day of the week
%u Week (00..53), where Monday is the first day of the week
%V Week (01..53), where Sunday is the first day of the week; used with %X
%v Week (01..53), where Monday is the first day of the week; used with %x
%% A literal `%'.
All other characters are just copied to the result without interpretation. The %f format specifier is available as of MySQL 4.1.1. As of MySQL Version 3.23, the `%' character is required before format specifier characters. In earlier versions of MySQL, `%' was optional. The reason the ranges for the month and day specifiers begin with zero is that MySQL allows incomplete dates such as '2004-00-00' to be stored as of MySQL 3.23.
mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00', '%W %M %Y');
        -> 'Saturday October 1997'
mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00', '%H:%i:%s');
        -> '22:23:00'
mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00',
                          '%D %y %a %d %m %b %j');
        -> '4th 97 Sat 04 10 Oct 277'
mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00',
                          '%H %k %I %r %T %S %w');
        -> '22 22 10 10:23:00 PM 22:23:00 00 6'
mysql> SELECT DATE_FORMAT('1999-01-01', '%X %V');
        -> '1998 52'
DAY(date)
DAY() is a synonym for DAYOFMONTH(). It is available as of MySQL 4.1.1. 
DAYNAME(date)
Returns the name of the weekday for date:
mysql> SELECT DAYNAME('1998-02-05');
        -> 'Thursday'
DAYOFMONTH(date)
Returns the day of the month for date, in the range 1 to 31:
mysql> SELECT DAYOFMONTH('1998-02-03');
        -> 3
DAYOFWEEK(date)
Returns the weekday index for date (1 = Sunday, 2 = Monday, ... 7 = Saturday). These index values correspond to the ODBC standard.
mysql> SELECT DAYOFWEEK('1998-02-03');
        -> 3
DAYOFYEAR(date)
Returns the day of the year for date, in the range 1 to 366:
mysql> SELECT DAYOFYEAR('1998-02-03');
        -> 34
EXTRACT(type FROM date)
The EXTRACT() function uses the same kinds of interval type specifiers as DATE_ADD() or DATE_SUB(), but extracts parts from the date rather than performing date arithmetic.
mysql> SELECT EXTRACT(YEAR FROM "1999-07-02");
       -> 1999
mysql> SELECT EXTRACT(YEAR_MONTH FROM "1999-07-02 01:02:03");
       -> 199907
mysql> SELECT EXTRACT(DAY_MINUTE FROM "1999-07-02 01:02:03");
       -> 20102
mysql> SELECT EXTRACT(MICROSECOND FROM "2003-01-02 10:30:00.00123");
        -> 123
FROM_DAYS(N)
Given a daynumber N, returns a DATE value:
mysql> SELECT FROM_DAYS(729669);
        -> '1997-10-07'
FROM_DAYS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it doesn't take into account the days that were lost when the calendar was changed. 
FROM_UNIXTIME(unix_timestamp)
 
FROM_UNIXTIME(unix_timestamp,format)
Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT FROM_UNIXTIME(875996580);
        -> '1997-10-04 22:23:00'
mysql> SELECT FROM_UNIXTIME(875996580) + 0;
        -> 19971004222300
If format is given, the result is formatted according to the format string. format may contain the same specifiers as those listed in the entry for the DATE_FORMAT() function:
mysql> SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(),
    ->                      '%Y %D %M %h:%i:%s %x');
        -> '2003 6th August 06:22:58 2003'
GET_FORMAT(DATE | TIME | TIMESTAMP, 'EUR' | 'USA' | 'JIS' | 'ISO' | 'INTERNAL')
Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions, and when setting the server variables DATE_FORMAT, TIME_FORMAT, and DATETIME_FORMAT. The three possible values for the first argument and the five possible values for the second argument result in 15 possible format strings (for the specifiers used, see the table in the DATE_FORMAT() function description):
Function call Result
GET_FORMAT(DATE,'USA') '%m.%d.%Y'
GET_FORMAT(DATE,'JIS') '%Y-%m-%d'
GET_FORMAT(DATE,'ISO') '%Y-%m-%d'
GET_FORMAT(DATE,'EUR') '%d.%m.%Y'
GET_FORMAT(DATE,'INTERNAL') '%Y%m%d'
GET_FORMAT(TIMESTAMP,'USA') '%Y-%m-%d-%H.%i.%s'
GET_FORMAT(TIMESTAMP,'JIS') '%Y-%m-%d %H:%i:%s'
GET_FORMAT(TIMESTAMP,'ISO') '%Y-%m-%d %H:%i:%s'
GET_FORMAT(TIMESTAMP,'EUR') '%Y-%m-%d-%H.%i.%s'
GET_FORMAT(TIMESTAMP,'INTERNAL') '%Y%m%d%H%i%s'
GET_FORMAT(TIME,'USA') '%h:%i:%s %p'
GET_FORMAT(TIME,'JIS') '%H:%i:%s'
GET_FORMAT(TIME,'ISO') '%H:%i:%s'
GET_FORMAT(TIME,'EUR') '%H.%i.%S'
GET_FORMAT(TIME,'INTERNAL') '%H%i%s'
ISO format is ISO 9075, not ISO 8601.
mysql> SELECT DATE_FORMAT('2003-10-03', GET_FORMAT(DATE, 'EUR')
        -> '03.10.2003'
mysql> SELECT STR_TO_DATE('10.31.2003', GET_FORMAT(DATE, 'USA'))
        -> 2003-10-31
mysql> SET DATE_FORMAT=GET_FORMAT(DATE, 'USA'); SELECT '2003-10-31';
        -> 10-31-2003
GET_FORMAT() is available as of MySQL 4.1.1. See See section 5.5.6 SET Syntax
HOUR(time)
Returns the hour for time. The range of the return value will be 0 to 23 for time-of-day values:
mysql> SELECT HOUR('10:05:03');
        -> 10
However, the range of TIME values actually is much larger, so HOUR can return values greater than 23:
mysql> SELECT HOUR('272:59:59');
        -> 272
LAST_DAY(date)
Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid.
mysql> SELECT LAST_DAY('2003-02-05'), LAST_DAY('2004-02-05');
        -> '2003-02-28', '2004-02-29'
mysql> SELECT LAST_DAY('2004-01-01 01:01:01');
        -> '2004-01-31'
mysql> SELECT LAST_DAY('2003-03-32');
        -> NULL
LAST_DAY() is available as of MySQL 4.1.1. 
LOCALTIME
 
LOCALTIME()
LOCALTIME and LOCALTIME() are synonyms for NOW()
LOCALTIMESTAMP
 
LOCALTIMESTAMP()
LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW()
MAKEDATE(year,dayofyear)
Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result will NULL.
mysql> SELECT MAKEDATE(2001,31), MAKEDATE(2001,32);
        -> '2001-01-31', '2001-02-01'
mysql> SELECT MAKEDATE(2001,365), MAKEDATE(2004,365);
        -> '2001-12-31', '2004-12-30'
mysql> SELECT MAKEDATE(2001,0);
        -> NULL
MAKEDATE() is available as of MySQL 4.1.1. 
MAKETIME(hour,minute,second)
Returns a time value calculated from the hour, minute, and second arguments.
mysql> SELECT MAKETIME(12,15,30);
        -> '12:15:30'
MAKETIME() is available as of MySQL 4.1.1. 
MICROSECOND(expr)
Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999.
mysql> SELECT MICROSECOND('12:00:00.123456');
        -> 123456
mysql> SELECT MICROSECOND('1997-12-31 23:59:59.000010');
        -> 10
MICROSECOND() is available as of MySQL 4.1.1. 
MINUTE(time)
Returns the minute for time, in the range 0 to 59:
mysql> SELECT MINUTE('98-02-03 10:05:03');
        -> 5
MONTH(date)
Returns the month for date, in the range 1 to 12:
mysql> SELECT MONTH('1998-02-03');
        -> 2
MONTHNAME(date)
Returns the name of the month for date:
mysql> SELECT MONTHNAME('1998-02-05');
        -> 'February'
NOW()
Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT NOW();
        -> '1997-12-15 23:50:26'
mysql> SELECT NOW() + 0;
        -> 19971215235026
PERIOD_ADD(P,N)
Adds N months to period P (in the format YYMM or YYYYMM). Returns a value in the format YYYYMM. Note that the period argument P is not a date value:
mysql> SELECT PERIOD_ADD(9801,2);
        -> 199803
PERIOD_DIFF(P1,P2)
Returns the number of months between periods P1 and P2. P1 and P2 should be in the format YYMM or YYYYMM. Note that the period arguments P1 and P2 are not date values:
mysql> SELECT PERIOD_DIFF(9802,199703);
        -> 11
QUARTER(date)
Returns the quarter of the year for date, in the range 1 to 4:
mysql> SELECT QUARTER('98-04-01');
        -> 2
SECOND(time)
Returns the second for time, in the range 0 to 59:
mysql> SELECT SECOND('10:05:03');
        -> 3
SEC_TO_TIME(seconds)
Returns the seconds argument, converted to hours, minutes, and seconds, as a value in 'HH:MM:SS' or HHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT SEC_TO_TIME(2378);
        -> '00:39:38'
mysql> SELECT SEC_TO_TIME(2378) + 0;
        -> 3938
STR_TO_DATE(str,format)
This is the reverse function of the DATE_FORMAT() function. It takes a string str, and a format string format, and returns a DATETIME value. The date, time, or datetime values contained in str should be given in the format indicated by format. For the specifiers that can be used in format, see the table in the DATE_FORMAT() function description. All other characters are just taken verbatim, thus not being interpreted. If str contains an illegal date, time, or datetime value, STR_TO_DATE() returns NULL.
mysql> SELECT STR_TO_DATE('03.10.2003 09.20', '%d.%m.%Y %H.%i')
        -> 2003-10-03 09:20:00
mysql> SELECT STR_TO_DATE('10rap', '%crap')
        -> 0000-10-00 00:00:00
mysql> SELECT STR_TO_DATE('2003-15-10 00:00:00', '%Y-%m-%d %H:%i:%s')
        -> NULL
STR_TO_DATE() is available as of MySQL 4.1.1. 
SUBDATE(date,INTERVAL expr type)
 
SUBDATE(expr,days)
When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB().
mysql> SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
        -> '1997-12-02'
mysql> SELECT SUBDATE('1998-01-02', INTERVAL 31 DAY);
        -> '1997-12-02'
As of MySQL 4.1.1, the second syntax is allowed, where expr is a date or datetime expression and days is the number of days to be subtracted from expr.
mysql> SELECT SUBDATE('1998-01-02 12:00:00', 31);
        -> '1997-12-02 12:00:00'
SUBTIME(expr,expr2)
SUBTIME() subtracts expr2 from expr and returns the result. expr is a date or datetime expression, and expr2 is a time expression.
mysql> SELECT SUBTIME("1997-12-31 23:59:59.999999", "1 1:1:1.000002");
        -> '1997-12-30 22:58:58.999997'
mysql> SELECT SUBTIME("01:00:00.999999", "02:00:00.999998");
        -> '-00:59:59.999999'
SUBTIME() was added in MySQL 4.1.1. 
SYSDATE()
SYSDATE() is a synonym for NOW()
TIME(expr)
Extracts the time part of the time or datetime expression expr.
mysql> SELECT TIME('2003-12-31 01:02:03');
        -> '01:02:03'
mysql> SELECT TIME('2003-12-31 01:02:03.000123');
        -> '01:02:03.000123'
TIME() is available as of MySQL 4.1.1. 
TIMEDIFF(expr,expr2)
TIMEDIFF() returns the time between the start time expr and the end time expr2. expr and expr2 are time or date-and-time expressions, but both must be of the same type.
mysql> SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001');
        -> '-00:00:00.000001'
mysql> SELECT TIMEDIFF('1997-12-31 23:59:59.000001','1997-12-30 01:01:01.000002');
        -> '46:58:57.999999'
TIMEDIFF() was added in MySQL 4.1.1. 
TIMESTAMP(expr)
 
TIMESTAMP(expr,expr2)
With one argument, returns the date or datetime expression expr as a datetime value. With two arguments, adds the time expression expr2 to the date or datetime expression expr and returns a datetime value.
mysql> SELECT TIMESTAMP('2003-12-31');
        -> '2003-12-31 00:00:00'
mysql> SELECT TIMESTAMP('2003-12-31 12:00:00','12:00:00');
        -> '2004-01-01 00:00:00'
TIMESTAMP() is available as of MySQL 4.1.1. 
TIME_FORMAT(time,format)
This is used like the DATE_FORMAT() function, but the format string may contain only those format specifiers that handle hours, minutes, and seconds. Other specifiers produce a NULL value or 0. If the time value contains an hour part that is greater than 23, the %H and %k hour format specifiers produce a value larger than the usual range of 0..23. The other hour format specifiers produce the hour value modulo 12:
mysql> SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
        -> '100 100 04 04 4'
TIME_TO_SEC(time)
Returns the time argument, converted to seconds:
mysql> SELECT TIME_TO_SEC('22:23:00');
        -> 80580
mysql> SELECT TIME_TO_SEC('00:39:38');
        -> 2378
TO_DAYS(date)
Given a date date, returns a daynumber (the number of days since year 0):
mysql> SELECT TO_DAYS(950501);
        -> 728779
mysql> SELECT TO_DAYS('1997-10-07');
        -> 729669
TO_DAYS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it doesn't take into account the days that were lost when the calendar was changed. 
UNIX_TIMESTAMP()
 
UNIX_TIMESTAMP(date)
If called with no argument, returns a Unix timestamp (seconds since '1970-01-01 00:00:00' GMT) as an unsigned integer. If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' GMT. date may be a DATE string, a DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or YYYYMMDD in local time:
mysql> SELECT UNIX_TIMESTAMP();
        -> 882226357
mysql> SELECT UNIX_TIMESTAMP('1997-10-04 22:23:00');
        -> 875996580
When UNIX_TIMESTAMP is used on a TIMESTAMP column, the function returns the internal timestamp value directly, with no implicit ``string-to-Unix-timestamp'' conversion. If you pass an out-of-range date to UNIX_TIMESTAMP() it returns 0, but please note that only basic checking is performed (year 1970-2037, month 01-12, day 01-31). If you want to subtract UNIX_TIMESTAMP() columns, you may want to cast the result to signed integers. See section 6.3.5 Cast Functions
UTC_DATE
 
UTC_DATE()
Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context:
mysql> SELECT UTC_DATE(), UTC_DATE() + 0;
        -> '2003-08-14', 20030814
UTC_DATE() is available as of MySQL 4.1.1. 
UTC_TIME
 
UTC_TIME()
Returns the current UTC time as a value in 'HH:MM:SS' or HHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT UTC_TIME(), UTC_TIME() + 0;
        -> '18:07:53', 180753
UTC_TIME() is available as of MySQL 4.1.1. 
UTC_TIMESTAMP
 
UTC_TIMESTAMP()
Returns the current UTC date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS format, depending on whether the function is used in a string or numeric context:
mysql> SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
        -> '2003-08-14 18:08:04', 20030814180804
UTC_TIMESTAMP() is available as of MySQL 4.1.1. 
WEEK(date [,mode])
The function returns the week number for date. The two-argument form of WEEK() allows you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range 0-53 or 1-52. When mode argument is omitted the value of a default_week_format server variable (or 0 in MySQL 4.0 or earlier) is assumed. See section 5.5.6 SET Syntax. The following table demonstrates how the mode argument works:
Value Meaning
0 Week starts on Sunday; return value range is 0 to 53; week 1 is the first week that starts in this year
1 Week starts on Monday; return value range is 0 to 53; week 1 is the first week that has more than 3 days in this year
2 Week starts on Sunday; return value range is 1 to 53; week 1 is the first week that starts in this year
3 Week starts on Monday; return value range is 1 to 53; week 1 is the first week that has more than 3 days in this year
4 Week starts on Sunday; return value range is 0 to 53; week 1 is the first week that has more than 3 days in this year
5 Week starts on Monday; return value range is 0 to 53; week 1 is the first week that starts in this year
6 Week starts on Sunday; return value range is 1 to 53; week 1 is the first week that has more than 3 days in this year
7 Week starts on Monday; return value range is 1 to 53; week 1 is the first week that starts in this year
The mode value of 3 can be used as of MySQL 4.0.5. The mode value of 4 and above can be used as of MySQL 4.0.17.
mysql> SELECT WEEK('1998-02-20');
        -> 7
mysql> SELECT WEEK('1998-02-20',0);
        -> 7
mysql> SELECT WEEK('1998-02-20',1);
        -> 8
mysql> SELECT WEEK('1998-12-31',1);
        -> 53
Note: In Version 4.0, WEEK(date,0) was changed to match the calendar in the USA. Before that, WEEK() was calculated incorrectly for dates in USA. (In effect, WEEK(date) and WEEK(date,0) was incorrect for all cases.) Note that if a date falls in the last week of the previous year, MySQL will return 0 if you don't use 2, 3, 6, or 7 as the optional mode argument:
mysql> SELECT YEAR('2000-01-01'), WEEK('2000-01-01',0);
        -> 2000, 0
One might argue that MySQL should return 52 for the WEEK() function, because the given date actually occurs in the 52nd week of 1999. We decided to return 0 instead as we want the function to return ``the week number in the given year.'' This makes the usage of the WEEK() function reliable when combined with other functions that extract a date part from a date. If you would prefer the result to be evaluated with respect to the year that contains the first day of the week for the given date, you should use 2, 3, 6, or 7 as the optional mode argument.
mysql> SELECT WEEK('2000-01-01',2);
        -> 52
Alternatively, use the YEARWEEK() function:
mysql> SELECT YEARWEEK('2000-01-01');
        -> 199952
mysql> SELECT MID(YEARWEEK('2000-01-01'),5,2);
        -> '52'
WEEKDAY(date)
Returns the weekday index for date (0 = Monday, 1 = Tuesday, ... 6 = Sunday):
mysql> SELECT WEEKDAY('1998-02-03 22:23:00');
        -> 1
mysql> SELECT WEEKDAY('1997-11-05');
        -> 2
WEEKOFYEAR(date)
Returns the calendar week of the date as a number in the range from 1 to 53.
mysql> SELECT WEEKOFYEAR('1998-02-20');
        -> 8
WEEKOFYEAR() is available as of MySQL 4.1.1. 
YEAR(date)
Returns the year for date, in the range 1000 to 9999:
mysql> SELECT YEAR('98-02-03');
        -> 1998
YEARWEEK(date)
 
YEARWEEK(date,start)
Returns year and week for a date. The start argument works exactly like the start argument to WEEK(). Note that the year in the result may be different from the year in the date argument for the first and the last week of the year:
mysql> SELECT YEARWEEK('1987-01-01');
        -> 198653
Note that the week number is different from what the WEEK() function would return (0) for optional arguments 0 or 1, as WEEK() then returns the week in the context of the given year.

 

 

  

Recovering from SHDH4

Blog
This morning started with a really loud, jarring phone ring, from not my phone, followed by a muffled conversation, followed by a wild haired, sleepy eyed, not-quite-sober looking attempt at standing up by my fellow all-nighter at SHDH (Mom: it was an overnight programming event where 60+ developers and designers descended on a house in the evening and programmed, designed, presented work, shared ideas, and socialized until the early hours).

My conversation with said guy:

me:  Are you sober?
him:  A good question, Kitt.
me:  And?
him:  The short answer is, "No." But I think I'm sober enough to drive.
me:  Doesn't the first answer negate the second one?
him:  blank stare

Um...

Yeah.

11 of us crashed at the SHDH, waking up the this morning to a smaller morning geek fest, with 8 of us huddled around the tables on laptops, sharing even more geek moments.

Eventually, calls for food overrode all entertainment, and the remaining 10 of us (Jeff, David, Lloyd, Messina, Tantek, Dani, Eris, Andy, Adam and me) drove to Buck's (south! closer to home for me!) for breakfast/lunch. Had an entertaining conversation about procreation with David, allowing my completely non-traditional views on children to filter out. David tried to explain (at my request) his the desire to have children: wanting to raise a mini-me, influencing positively another life, validating oneself through gene propogation. I think fundamentally if that desire is missing, all the reasons in the world aren't going to make it appear. David did point out, in a gentle non-judgemental way, however, how shallow my reasons for not wanting children are.

I took no pictures this weekend, which is a little odd.

Low point of the night: realizing Andy had just rebooted my laptop, and I hadn't saved its session state in any meaningful, recoverable way.

High point of the night: wrastling said laptop from the evil clutches of Andy and Cal as they attempted to both root it, and install the hello program on it that I really, really didn't want.

General impressions of the evening: had a great time, though the saying "You get out of life what you put into it," comes to mind. I had wanted to program in a code-jam scenario, but I spent more time socializing and less time actually programming than I wanted. Which is unfortunate given the level of expertise in that house last night. I think the large number of people made it more social, less tech, and had the numbers been around 20-30, more coding would have been done (by me, unsure in general).

Enjoyed meeting and talking to Elliot and Jesse and Adam and Bryan and Cal (though I'd actually met Cal before at the Carson Workshop in June, as he's the one that presented - Mike pointed out to me that I totally blown off Messina and Ryan King at lunch at that workshop to work on the pagination module during lunch - Andy pointed out he showed up for the bar meeting afterward). I especially liked Alex Russell's Dojo presentation. I'm terribly inspired to add it to the UPA's online rostering system.

Right after I finish up a couple of Messina's demos.

Journey to Vim

Blog
Okay, here we go.

Done did got me my binaries.

And a tutorial.

And, in theory anyway, a reasonable setup from Andy (theory only in as much as I have nothing to compare it to, but I'm sure it's beautiful).

QS rescanned my dirs, so it opens with three keystrokes.

So.

Yeah.

I'm all set.

Mike is just going to love this when he starts hearing my cursing from across the office when I use the wrong editing strokes.

VIM!

Blog
Heh.

That would be me.

Knee-deep in Java

Blog
I'm knee deep in Java for the first time in a year and a half. Much to my surprise, it's interesting. And even more surprising is that I'm able to follow the client's environment setup. Mike purchased a new development system (Windows XP, bleh), and setting it up has been a bear, but I have to think that's more because of the OS, and less because of the development environment.

The only issues I've had have been not recalling all the setup steps before hand. Instead, I'll do a step, look at the results, realize, oh yeah, I forgot this other step, adjust it, and keep going.

Well, that and the firewall blocking each and every system request. After about an hour, I gave up and just disabled the thing.

So, yeah, it's nice to be able to make progress with the development environment I struggled with years (5 years!) ago.

Of course, Kris can fix any of my problems in five minutes.

Five minutes!

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