问题
I need a standard deviation function in SQLite. I have found one here:
http://www.sqlite.org/contrib?orderby=date
but its part of an extension file to SQLite. I've never installed one of these before and I don't know how to. I found this existing function, load_extension, at http://www.sqlite.org/lang_corefunc.html, but I don't understand what the parameters X and Y are.
Basically, I need someone to give me a step by step guide on how to install the aggregate extension file. Can anyone do this?
回答1:
SQLite extensions are libraries with dynamic linkage. You can find some examples here (This is a fossil repository, click on “login/fill captcha” to enable hyperlinks). See for example md5.c.
load_extension
must be enabled in SQLite (pragma IIRC)- it requires as first argument the path of the library
- The second argument is the name of the entry point function (in md5.c it is
sqlite3_extension_init
). Its prototype must beint(sqlite3*, char **, const sqlite3_api_routines *)
. - In SQL you can try
SELECT load_extension('md5.so', 'sqlite3_extension_init');
or simplySELECT load_extension('md5.so');
You can try to compile md5.c
, and from the sqlite shell use .load md5.so
来源:https://stackoverflow.com/questions/6663124/how-to-load-extensions-into-sqlite