SELECT and testing condition of a field in the last 2 lines of rows

[philippe Cadic]

Hello all.
I'm relatively new to complexe select queries. I could solve the problem in PERL with a heavy solution, I'm looking for a more elegant and fast MYSQL query solution, to improve speed. This script is a perl/mysql stock exchange robot attempt.


If have a table called: hbb_signals with the fields:
id_signal date_in time_in stock_code company_name last_quote last_pattern signal



With the following records in if (for example)

1241 2014-08-18 01:29:07 8296.HK SINO-LIFEGROUP 0.2490 BEARISH HANGING MAN STAY LONG

2487 2014-08-22 20:49:44 8296.HK SINO-LIFEGROUP 0.2450 BULLISH HOMING PIGEON BUY

691 2014-08-18 01:05:54 0992.HK LENOVO GROUP 11.5600 BEARISH ENGULFING STAY LONG

1939 2014-08-22 20:16:45 0992.HK LENOVO GROUP 11.8000 BEARISH MEETING LINE STAY LONG

I would like to do the following.
make a SELECT query and sort the stock code value + signal value, only if today's signal and yesterday's signal have changed. In example upper here, the result would clear LENOVO / 0992.HK stock lines because SIGNAL field has no change in the last 2 days. the result would only display SINO-LIFE GROUP / 8286/HK because SIGNAL field would not be egal yesterday and today.


There should be something like

SELECT (stock_quote, company_name) from dbb_signals where * signal of curdate() <> signal of curdate()-1 DAY *

Who could put me in the right direction with the select Query ?