MySQL – James Lin's Blog

New technology to crack down on house-flipping

James Lin — Thu, 09 Mar 2017 20:44:22 +0000

Just read an article on cracking down house flipping in NZ, it says “New Zealand’s real estate watchdog is ramping up its crackdown on house-flipping by investing in new technology which allows it to track when properties have been quickly re-sold for huge profits.”

So what’s the new technology is about? You would have thought there is a database table with a simple SQL query like this:

select * from sales_record r1 left join sales_record r2 on r1.title_no = r2.title_no and r1.id < r2.id where datediff(r2.sales_date, r1.sales_date) < 30;

Installing Python Mysql Adapter On Mac OSX

James Lin — Mon, 11 Feb 2013 18:40:42 +0000

First download and install mysql for Mac OSX
Install virtualenv, create a virtualenv and activate it
Pip install mysql-python, and you will see an error “EnvironmentError: mysql_config not found”
Find the mysql_config by running “sudo find / -name ‘mysql_config'”
Go to your /path to virtualenv/build/mysql-python
Edit site.cfg
Uncomment this line “#mysql_config = /usr/local/bin/mysql_config” and change the path to what you found in step 4
Then run “python setup.py install”
if you get “Library not loaded: libmysqlclient.18.dylib” when using the adapter
Then symlink this file: “sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib”

To control the server:

sudo /Library/StartupItems/MySQLCOM/MySQLCOM stop
sudo /Library/StartupItems/MySQLCOM/MySQLCOM start
sudo /Library/StartupItems/MySQLCOM/MySQLCOM restart

MySQL locate function

James Lin — Wed, 29 Feb 2012 20:28:32 +0000

So everyone knows sql LIKE to search wildcard matches the criteria. How about in a situation that you need to return all the rows that has value is part of the criteria string.

eg. given a full URL http://www.abc.com/bl/abcdefg/, return all the rows with uri_part field that values are part of the URL string.

+------------+
|uri_part    |
+------------+
|/bl/        |
|/bl/abc/    |
|/ba/abc/    |
+------------+

Normally LIKE statement works on the other way around, so you need to use LOCATE function. So in this example would be:

SELECT uri_part FROM table WHERE locate(uri_part, 'http://www.abc.com/bl/abcdefg/');