"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." (Robert A. Heinlein)

Friday 31 October 2008

Populating a table with random people


It happened I had  to  fill a table with realistic but not real people data.Here how did I managed it (ported to MySQL sintax).
First lets create a people table like this :
CREATE TABLE PEOPLE(NAME VARCHAR(20),
                                     SURNAME VARCHAR(20),
                                     SEX VARCHAR(1),
                                     DOB DATE);
Then create tables with sample names and surnames:
CREATE TABLE NAMES(NAME VARCHAR(20), SEX VARCHAR(1));
CREATE TABLE SURNAMES(SURNAME VARCHAR(20));
And fill them with some values:
INSERT INTO NAMES(NAME,SEX) VALUES('Jhon','M');
INSERT INTO NAMES(NAME,SEX) VALUES('Jack','M');
INSERT INTO NAMES(NAME,SEX) VALUES('Jeff','M');
INSERT INTO NAMES(NAME,SEX) VALUES('Judy','F');
INSERT INTO NAMES(NAME,SEX) VALUES('Jade','F');
INSERT INTO NAMES(NAME,SEX) VALUES('Jane','F');
INSERT INTO SURNAMES(SURNAME) VALUES('Red');
INSERT INTO SURNAMES(SURNAME) VALUES('White');
INSERT INTO SURNAMES(SURNAME) VALUES('Green');
Now we'll be able to get a single random person with a query like this:
SELECT NAME, SEX,
           CURDATE() - INTERVAL RAND()*365.25*100 DAY AS DOB,
                 (SELECT SURNAME FROM SURNAMES ORDER BY RAND() LIMIT 1) AS SURNAME
FROM NAMES ORDER BY RAND() LIMIT 1;
We can write a simple procedure to populate the table with the desired number of rows:
CREATE PROCEDURE FILL(IN NUM INT)
   BEGIN
       WHILE NUM > 0 DO
          INSERT INTO PEOPLE(NAME,SEX,DOB,SURNAME)
          SELECT NAME, SEX,
                            CURDATE() - INTERVAL RAND()*365.25*100 DAY AS DOB,
                         (SELECT SURNAME FROM SURNAMES ORDER BY RAND() LIMIT 1) AS SURNAME
         FROM NAMES ORDER BY RAND() LIMIT 1;
         SET NUM = NUM-1;
      END WHILE;
END;
We can call this procedure like this:
mysql> call FILL(10000);
Query OK, 1 row affected (40.73 sec)
A ten thousand people population in forty seconds (on PIII at 550Mz) is not bad.
Of course many improvements can be done like adding a random place of birth (based on a table of places) or making date of birth distribution more realistic.

Thursday 23 October 2008

Hello world!

Here I am, at last, my first post ...
After wrestling with my own indecision about choosing the right style, pictures and colours. After writing copying a suitable disclaimer I have no more excuses for not to start writing my first post.
 I'm going to write, in this blog, about my personal programming experiments: I'm 40 but I'm still studing, and learning, everyday. Not surprising if you think how many frameworks, libraries and programming tools are published on the net nowdays.
 What else? Hello world!
public class HelloWorld {     
    public static void main(String[] args)     {         
         System.out.println
("Hello World!");
    }
}
 P.S.
If you are interested in posting java code bits in your blog have a look at Java2Html.