-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 08/02/12 01:47, Steinar Midtskogen wrote: > OK. But then I wont have an SQL interface for accessing interpolated > data. It's acceptable. An SQL interface is mostly a "nice to have", > so I could do some quick queries in SQL instead of having to write C > code for it.
Making SQL functions that call your C code will do the trick. Also do you know how easy it is to add a SQL shell to your C code? Read a line of input and call sqlite3_complete on it. If not complete, read another line appending to earlier line and call sqlite3_complete again. Rinse and repeat until you have a complete line then prepare, step and output whatever it returns. > So, if I go for that approach, you'd recommend that I add functions, > such as "reading", and if I want a mean temperature, I should add a > function "mean" and not try to change what AVG will do? Functions you add to SQLite do not have to work on tables mentioned in the query. The doc is a little confusing: http://www.sqlite.org/c3ref/create_function.html You need to implement the xFunc callback which is like main() in taking a count of arguments and their values. Once decoded just call your existing C function. Only you know the nature of missing data, how often it is missing, the calculations you want to do and how all this affects the final conclusions you are generating from the data. (You could also fix the data generator to synthesize missing values rather than trying to fix it later.) If you are working with shorter periods (eg a day) then you can also create temporary tables putting in the missing values. But if you absolutely need every value to be present for arbitrary SQL queries then virtual tables will pretty much be the only transparent thing. Roger -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEARECAAYFAk8yxmUACgkQmOOfHg372QTN/gCguW0ld/UZxFmjVcLMGFMt88ip Hz0AoMbgJFwoNXw5DvwLFPe02WCh2Ok1 =C71Q -----END PGP SIGNATURE----- _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
