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From: Gareth Evans <donotspam@fastmail.fm>
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Subject: Re: A situation with one parent table and 3 child tables
Date: Mon, 2 Oct 2023 22:46:00 +0100
Message-Id: <0C0B8C3D-D729-4916-B105-0FF998D4D2D4@fastmail.fm>
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To: JORGE MALDONADO <jorgemal1960@gmail.com>
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Hi Jorge,

Several 1:m relationships may be appropriate where the number of correspondi=
ng records on the m side can be 0, 1 or more.

If the child entities vary little or not at all in structure, but represent d=
ifferent =E2=80=9Ctypes=E2=80=9D, a single 1:m might suffice with =E2=80=9Ct=
ype=E2=80=9D as an attribute at the many end, and suitable indexes, and filt=
ering at the application level.

It's difficult to generalise.  If you can give more information on the scena=
rio, better advice may be forthcoming.

Kind regards,
Gareth


> On 2 Oct 2023, at 21:59, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
>=20
> =EF=BB=BF
> Hi,
>=20
> I have one parent table (table_p) with 3 child tables (table_ch1, table_ch=
2 and table_ch3). Each record of the parent table can be associated with 1 a=
nd only 1 child table records. This means that:
>=20
> * Some records of the table_p will link to records of table_ch1
> * Some records of the table_p will link to records of table_ch2
> * Some records of the table_p will link to records of table_ch3
>=20
> At first look, this does not make very much sense to me. I thought about c=
onsidering 3 parent tables, one for each child table. However, the 3 parent t=
ables would have the same exact structure and I would like to know if there i=
s a workaround for this issue.
>=20
> Thanks in advance.
>=20
> Jorge Maldonado

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div dir=3D"ltr"></div><div dir=3D"ltr">Hi J=
orge,</div><div dir=3D"ltr"><br></div><div dir=3D"ltr">Several 1:m relations=
hips may be appropriate where the number of corresponding records on the m s=
ide can be 0, 1 or more.</div><div dir=3D"ltr"><br></div><div dir=3D"ltr">If=
 the child entities vary little or not at all in structure, but represent di=
fferent =E2=80=9Ctypes=E2=80=9D, a single 1:m might suffice with =E2=80=9Cty=
pe=E2=80=9D as an attribute at the many end, and suitable indexes, and filte=
ring at the application level.</div><div dir=3D"ltr"><br></div><div dir=3D"l=
tr">It's difficult to generalise. &nbsp;If you can give more information on t=
he scenario, better advice may be forthcoming.</div><div dir=3D"ltr"><br></d=
iv><div dir=3D"ltr">Kind regards,</div><div dir=3D"ltr">Gareth</div><div dir=
=3D"ltr"><br></div><div dir=3D"ltr"><br><div dir=3D"ltr"></div><blockquote t=
ype=3D"cite">On 2 Oct 2023, at 21:59, JORGE MALDONADO &lt;jorgemal1960@gmail=
.com&gt; wrote:<br><br></blockquote></div><blockquote type=3D"cite"><div dir=
=3D"ltr">=EF=BB=BF<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr">Hi,<div=
><br></div><div>I have one parent table (<b>table_p</b>) with 3 child tables=
 (<b>table_ch1</b>, <b>table_ch2 </b>and <b>table_ch3</b>). Each record of t=
he parent table can be associated with 1 and only 1 child table records. Thi=
s means that:</div><div><br></div><div>* Some records of the <b>table_p</b> w=
ill link to records of <b>table_ch1</b></div><div>* Some records of the <b>t=
able_p</b> will link to records of <b>table_ch2</b><br></div><div>* Some rec=
ords of the <b>table_p</b> will link to records of <b>table_ch3</b><br></div=
><div><br></div><div>At first look, this does not make very much sense to me=
. I thought about considering 3 parent tables, one for each child table. How=
ever, the 3 parent tables would have the same exact structure and I would li=
ke to know if there is a workaround&nbsp;for this issue.</div><div><br></div=
><div>Thanks in advance.</div><div><br></div><div>Jorge Maldonado</div></div=
></div></div>
</div></blockquote></body></html>=

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