Keith Medcalf, on Monday, November 18, 2019 04:27 PM, wrote...
>
> This relies on two implementation details particular to SQLite3 which hold>
> at present,
> but may of course change at any time:
> (1) that selecting a non-aggregate scalar column will return a value from
> (one of) the
> row(s) matching the value of the aggregate (most RDBMS used to do this, most
> now throw
> an error at this construct); and,
> (2) that the optimizer will not optimize "IfNull('p006', max(idate))" into
> 'p006' since
> the result must always be 'p006' which would of course render the select to
> be a simple
> select and not an aggregate causing "all hell to break loose".
Thanks Keith. So, you are saying that this is a bad INSERT, and I don't know
much to argue, but is working. If I take out the first IfNull, and there is
not, at least one instance of 'p006' in the table, the INSERT never works. I
was thinking of using COALESCE, but that would also mean that one or the other
would have to be not null. Any suggestion would be appreciated.
[clip]
> >SELECT IfNull('p006', Max(idate)),
> > IfNull(b, 1),
> > IfNull(c, 2),
> > 'y',
> > IfNull(e, 4),
> > '2019-20-12'
> > FROM t
> > WHERE a = 'p006';
> >
> >versus this:
> >SELECT (a,b,c,d,e,idate) from t where a = "p006"
> >
> >Doesn't the where clause that cannot be satisfied in both cases guarantee
> >that no rows will be selected, when there are no records in the database?
> >Doug
> >
> >> -----Original Message-----
> >> From: sqlite-users, on
Jose Isaias Cabrera
> >> Sent: Monday, November 18, 2019 12:11 PM
> >
> >> Subject: Re: [sqlite] Question about: Adding a record to a table
> >> with select failure
> >>
> >>
> >> Doug, on Monday, November 18, 2019 12:31 PM, wrote...
> >> Jose Isaias Cabrera
> >> [clip]
> >> > > >
> >> > > > INSERT INTO t (a, b, c, d, e, idate)
> >> > > > SELECT IfNull('p006', Max(idate)),
> >> > > > IfNull(b, 1),
> >> > > > IfNull(c, 2),
> >> > > > 'y',
> >> > > > IfNull(e, 4),
> >> > > > '2019-20-12'
> >> > > > FROM t
> >> > > > WHERE a = 'p006';
> >> >
> >> > I think that you will never insert the first record with a query
> >> like this, since
> >> > the select returns 0 records of there are none in the database
> >> yet.
> >>
> >> Well, it does...
> >> sqlite> create table t (a, b, c, d, e, idate, PRIMARY KEY(a,
> >> idate));
> >> sqlite> INSERT INTO t
> >> ...> SELECT IfNull('p001', Max(idate)),
> >> ...> IfNull(b, 1),
> >> ...> IfNull(c, 2),
> >> ...> IfNull(d,'n'),
> >> ...> IfNull(e, 4),
> >> ...> '2019-20-11'
> >> ...> FROM t
> >> ...> WHERE a = 'p001';
> >> sqlite> select * from t;
> >> p001|1|2|n|4|2019-20-11
> >> sqlite>
> >>
> >> And, since I put an uniqueness on a and idate, now these can not
> >> be repeated, so if I run the same command again,
> >> sqlite> INSERT INTO t
> >> ...> SELECT IfNull('p001', Max(idate)),
> >> ...> IfNull(b, 1),
> >> ...> IfNull(c, 2),
> >> ...> IfNull(d,'n'),
> >> ...> IfNull(e, 4),
> >> ...> '2019-02-11'
> >> ...> FROM t
> >> ...> WHERE a = 'p001';
> >> Error: UNIQUE constraint failed: t.a, t.idate
> >> sqlite>
> >>
> >> I do not get a repeated record for 'p001' and 2019-02-11; But if
> >> they are different,
> >> sqlite> INSERT INTO t
> >> ...> SELECT IfNull('p002', Max(idate)),
> >> ...> IfNull(b, 1),
> >> ...> IfNull(c, 2),
> >> ...> IfNull(d,'n'),
> >> ...> IfNull(e, 4),
> >> ...> '2019-02-11'
> >> ...> FROM t
> >> ...> WHERE a = 'p002';
> >> sqlite> select * from t;
> >> p001|1|2|n|4|2019-02-11
> >> p002|1|2|n|4|2019-02-11
> >>
> >> It'll work. Thanks.
> >>
> >> josé
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