Ertan,
You should read https://www.sqlite.org/datatype3.html#section_2 if you haven't
already.
SQLite has exactly 1 floating-point type, which is what you get no matter if you
say float/double/etc, and it is 8 bytes, which corresponds to a Double in most
programming languages.
You can't change what SQLite uses other than explicitly not using a
floating-point type; you have integer, float, blob, text, and that's it.
Therefore, if you use anything other than a double in your app, you will be
converting when storing or retrieving, which makes things slower and introduces
loss, hence I say use Double everywhere.
-- Darren Duncan
On 2016-07-05 4:34 PM, Ertan Küçükoğlu wrote:
Hardware that the application will run is ~1Ghz Atom CPU, ~1GB RAM, regular Laptop HDD
(no SSD). Time to time, there will be calculations, Network file transfer, and DLL
function calls (all three) will be simultaneously running. Application has Timers and
Socket listening components on it. My concern is to have a situation which
"seems" like an application freeze.
On the other hand, will it be any help to increase accuracy to use Currency (8
bytes fixed-point data type) in my application for Price and Total fields,
leave Amount field as Double?
Thanks.
-----Original Message-----
From: sqlite-users-boun...@mailinglists.sqlite.org
[mailto:sqlite-users-boun...@mailinglists.sqlite.org] On Behalf Of Darren Duncan
Sent: Wednesday, July 6, 2016 1:20 AM
To: SQLite mailing list <sqlite-users@mailinglists.sqlite.org>
Subject: Re: [sqlite] Currency & SQLite
On 2016-07-05 3:02 PM, Ertan Küçükoğlu wrote:
I am using Delphi 10 for programming. Current variables are defined as Double (8 bytes
real), saved in Database using something "DataSet.FieldByName('Amount').AsFloat :=
My_double_variable" However, I am now considering to convert all Double datatypes to
Single (4 bytes real) for performance issues.
Do NOT change to using Single, always use Double, end to end.
First of all, Double is what SQLite uses internally for floats, per its
documentation:
"The value is a floating point value, stored as an 8-byte IEEE floating point
number."
So if you're already using Double in your app then staying that way should
maintain accuracy, especially when you want accuracy for more than say 3-5
decimal digits in total.
Secondly, for financial applications, accuracy trumps performance. Converting
to Single at any time is just going to cause you trouble.
And really, are you sure using Single would actually help performance? Have
you measured it in a real workload? More likely on modern devices it won't be
any faster and you will have lost your accuracy for nothing.
-- Darren Duncan
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