On 3/2/18, J Decker <d3c...@gmail.com> wrote: > On Fri, Mar 2, 2018 at 4:19 AM, Richard Hipp <d...@sqlite.org> wrote: > >> On 3/2/18, Olivier Mascia <o...@integral.be> wrote: >> > >> > What values will be considered FALSE, and hence will TRUE be NOT FALSE >> > or >> > equality to some other specific value? >> >> I have a note to provide additional documentation on this before the >> release. >> >> In short, a value is FALSE is, when converted into a floating point >> number via CAST(x AS REAL) it has a value of 0.0. >> >> It used to be (https://www.sqlite.org/src/info/36fae083b450e3af) that >> sometimes FALSE was determined by CAST(x AS INTEGER). This was >> inconsistent. Beginning with 3.23.0, FALSE is determined by CAST(x AS >> REAL) in all cases. >> >> So in other words, it used to be that 0.5 was sometimes considered >> TRUE and other times considered FALSE, depending on context. It is >> now always considered TRUE. >> >> Strings are TRUE or FALSE depending on whether or not they evaluate to >> non-zero when converted. '123xyz' is TRUE, but '0abc', 'abc', and '' >> are all FALSE. >> >> >> > Will insert into T values(FALSE) actually store integer 0 no matter >> column >> > affinity or will it follow affinity? >> >> No. FALSE is merely an alias for 0. Affinity still applies. If the >> column is of type TEXT, then it will store '0', not 0. >> > > is NULL false?
No. NULL is neither TRUE nor FALSE. SQL (and SQLite) uses three-value logic. NULL is TRUE -> FALSE NULL is FALSE -> FALSE NULL is NULL -> TRUE TRUE is NULL -> FALSE TRUE is TRUE -> TRUE TRUE is FALSE -> FALSE FALSE is NULL -> FALSE FALSE is TRUE -> FALSE FALSE is FALSE -> TRUE Note the definition of the WHERE clause is that it causes all rows to be returned where the condition is TRUE. That means that it rejects cases where the condition is either FALSE or NULL. Likewise the CASE statement groups NULL together with FALSE for its binary decisions. I didn't invent this - it is the way SQL works. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
