Just execute the SQL containing the function. If the function does not exist
then you will get an error thrown when you attempt to prepare the statement
containing the function that does not exist ... and your application can parse
the error message and do the needful. Of course, just because the function x
exists doesn't mean that it is the function x that you want, merely that it is
a function named x ...
SQLite version 3.29.0 2019-05-22 23:12:10
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite> create table t(x);
sqlite> insert into t values (10),(20),(30),(40);
sqlite> create view v1 as select stdev(x) from t;
sqlite> create view v2 as select stddev(x) from t;
sqlite> select * from v1;
12.9099444873581
sqlite> select * from v2;
Error: no such function: stddev
---
The fact that there's a Highway to Hell but only a Stairway to Heaven says a
lot about anticipated traffic volume.
>-----Original Message-----
>From: sqlite-users [mailto:sqlite-users-
>boun...@mailinglists.sqlite.org] On Behalf Of Thomas Kurz
>Sent: Thursday, 23 May, 2019 00:58
>To: SQLite mailing list
>Subject: Re: [sqlite] SQL Features That SQLite Does Not Implement
>
>Ok, thank you for that hint. But it is still very unconvenient. How
>can I define a view based on your suggestion? I want to have
>something like
>
>CREATE VIEW foo AS SELECT {if has stddev then stddev(...) else null}
>FROM ...
>
>----- Original Message -----
>From: Keith Medcalf <kmedc...@dessus.com>
>To: SQLite mailing list <sqlite-users@mailinglists.sqlite.org>
>Sent: Thursday, May 23, 2019, 07:18:45
>Subject: [sqlite] SQL Features That SQLite Does Not Implement
>
>
>select name from pragma_function_list where name == 'M_Pi' collate
>nocase;
>
>returns the name of the function if it exists. See pragma
>function_list
>
>---
>The fact that there's a Highway to Hell but only a Stairway to Heaven
>says a lot about anticipated traffic volume.
>
>>-----Original Message-----
>>From: sqlite-users [mailto:sqlite-users-
>>boun...@mailinglists.sqlite.org] On Behalf Of Thomas Kurz
>>Sent: Wednesday, 22 May, 2019 22:19
>>To: SQLite mailing list
>>Subject: Re: [sqlite] SQL Features That SQLite Does Not Implement
>
>>I agree in that not every math function can be included by default.
>>My problem, however, is that I cannot know whether a user uses my
>>self-compiled version with built-in extension-functions.c, or a
>>downloaded version from sqlite.org.
>
>>It would be very, very helpful (especially regarding views!) to have
>>some kind of a "check function" so that one could write
>
>>SELECT CASE WHEN defined('stddev') THEN stddev(foo) ELSE NULL END
>>FROM bar
>
>
>>----- Original Message -----
>>From: Keith Medcalf <kmedc...@dessus.com>
>>To: SQLite mailing list <sqlite-users@mailinglists.sqlite.org>
>>Sent: Wednesday, May 22, 2019, 22:20:11
>>Subject: [sqlite] SQL Features That SQLite Does Not Implement
>
>
>>On Wednesday, 22 May, 2019 11:51, sky5w...@gmail.com wrote:
>
>>>Please add a note to the omitted page that many basic math
>functions
>>>are NOT supported. (sqrt,mod,power,stdev,etc.)
>
>>Traditionally "math library" functions provided by the various
>>language runtimes were not included becase this would introduce
>>dependancies on a "math library". While this is available on *most*
>>platforms, it is not available on *all* platforms which SQLite3 can
>>be compiled for out of the box. Furthermore the implementation of
>>some transcendentals may be intrinsic on some CPU's and require huge
>>amounts of library code on others. Statistical functions are not
>>included because, well, they require complex implementations to get
>>right.
>
>>Moreover, even the builtin functions are "lite" (the round function
>>does not round properly for instance (it does grade-school 4/5
>>rounding rather than half-even rounding), the average function is
>>rather simple in implementation and suffers from trivally triggered
>>sources of computational error (it uses sum/count rather than
>>successive approximation to the mean), and many other limitations
>>exist in the builtin implementations of many functions).
>
>>All of these issues can be "fixed" however, all you need to do is
>add
>>the necessary code via the extension mechanism to add whatever
>>functionality you require using whatever numerical methods you
>>determine are suitable for your needs. For example, I have added
>>default support via the extension mechanism (and the EXTRA_INIT
>hook)
>>to make all the distributed extensions available on every
>connection,
>>to add all the standard platform math functions, to add a bunch of
>>statistical functions, several platform APIs (Windows in this case),
>>and to "fix" the builtin round, datetime (to include proper support
>>for instant times and timezone manipulation using the standard IANA
>>timezone database), and added support for basic Unicode nocase and
>>noaccent collations without using the whole ICU library.
>
>>The downside of this is that the implementation of all these
>>"goodies" quadruples the size of the base engine code (sqlite3.obj)
>>and it is no longer "Lite". There are other drawbacks as well. For
>>example, it is difficult to make many advanced numerical calculation
>>methods (aggregates) compatible with window functions as currently
>>implemented.
>
>>About the only thing that is missing from SQLite3 is the ability to
>>declare and implement "user defined types" in a fully integrated way
>>(such as was added to DB2 back in the late 80's early 90's, and
>which
>>I do not think anyone else has implemented as nicely anywhere else).
>
>>Really, the issue is that SQLite3 is an SQL based relational storage
>>manager, and it implements this function very well. It does not
>>provide a huge array of accoutrements that you may see with other
>>more ex$pen$ive RDMS systems, but does provide the ability to add
>>(most of) those accoutrements if you wish.
>
>>---
>>The fact that there's a Highway to Hell but only a Stairway to
>Heaven
>>says a lot about anticipated traffic volume.
>
>
>
>
>
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>
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>
>
>
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