how do I fetch results with mysql for the past six months?

I have a basic query fetching results for all results earlier than today:

...where post_date < '"开发者_运维知识库.current_time('mysql')."'....

How do I only fetch results for the past 6 months, i.e.:

...where post_date > '".current_time('mysql')."' - 6 MONTHS && post_date < '".current_time('mysql')."'...

Use DATE_SUB (and GETDATE())

...where post_date > DATE_SUB(GETDATE(), INTERVAL 6 MONTH) ...

eg:

...  WHERE post_date > NOW() - INTERVAL 6 MONTH