Thread: FOREIGN KEY Reference on multiple columns

FOREIGN KEY Reference on multiple columns

From
Weiss, Jörg
Date:
<div class="WordSection1"><p class="MsoNormal">Hi!<p class="MsoNormal"> <p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US">Isit possible to create a “FOREIGN KEY CONSTRAINT” with references to multiple columns
ofthe reference table?</span><p class="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US"> </span><p
class="MsoNormal"><spanlang="EN-US" style="mso-ansi-language:EN-US">For example:</span><p class="MsoNormal"><span
lang="EN-US"style="mso-ansi-language:EN-US">Table <span class="SpellE"> parm</span>:</span><p class="MsoNormal"><span
lang="EN-US"style="mso-ansi-language:EN-US">CREATE TABLE <span class="SpellE">parm</span></span><p
class="MsoNormal"><spanlang="EN-US" style="mso-ansi-language:EN-US">(</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US"><spanstyle="mso-spacerun:yes">  </span>complex <span class="SpellE">varchar</span>(20)
NOTNULL,</span><p class="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US"><span style="mso-spacerun:yes"> 
</span>para<span class="SpellE">varchar</span>(50) NOT NULL,</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US"><spanstyle="mso-spacerun:yes">  </span>sort <span class="SpellE">int4</span> NOT NULL
DEFAULT10,</span><p class="MsoNormal"><span style="mso-spacerun:yes">  </span><span class="SpellE">value</span> <span
class="SpellE">varchar</span>(50)NULL,<span lang="EN-US" style="mso-ansi-language:EN-US"></span><p
class="MsoNormal"><spanlang="EN-US" style="mso-ansi-language:EN-US"><span style="mso-spacerun:yes"> </span>CONSTRAINT
<spanclass="SpellE">parm_pkey</span> PRIMARY KEY (complex, para, sort)</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US">)</span><pclass="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US"> </span><pclass="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US">Table
user</span><p class="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US">CREATE TABLE user</span><p
class="MsoNormal"><spanlang="EN-US" style="mso-ansi-language:EN-US">(</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US"><spanstyle="mso-spacerun:yes">  </span>name <span class="SpellE">varchar</span>(20) NOT
NULL,</span><pclass="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US"><span style="mso-spacerun:yes"> 
</span>typeinteger NULL</span><p class="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US">)</span><p
class="MsoNormal"><spanlang="EN-US" style="mso-ansi-language:EN-US"> </span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US">NowI want to create FOREIGN KEY on <span class="SpellE">user.type</span> with
referenceson <span class="SpellE">parm.value</span> and <span class="SpellE">param.para</span> WHERE <span
class="SpellE">param.para</span>= ‘<span class="SpellE">user_type</span>’</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US">Somethinglike this:</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US">ALTERTABLE user ADD CONSTRAINT <span class="SpellE">user_type_fkey</span> FOREIGN KEY
(type)REFERENCES <span class="SpellE"> parm</span> (<span class="SpellE">value,para</span>) WHERE <span
class="SpellE">parm.para</span>= '<span class="SpellE">user_type</span>';</span><p class="MsoNormal"><span lang="EN-US"
style="mso-ansi-language:EN-US"> </span><pclass="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US">Regards
…</span><pclass="MsoNormal"><span lang="EN-US" style="mso-ansi-language:EN-US"> </span><p class="MsoNormal"><span
lang="EN-US"style="mso-ansi-language:EN-US"> </span></div> 

Re: FOREIGN KEY Reference on multiple columns

From
Luca Vernini
Date:
2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> Hi!
Hi.

> Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
> multiple columns of the reference table?

Yes, it is.

see here:
http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
Section 5.3.5 there are some examples. One of them has multiple
columns, just like your case.

> Regards …

Regards.



Re: FOREIGN KEY Reference on multiple columns

From
Weiss, Jörg
Date:
> -----Ursprüngliche Nachricht-----
> Von: Luca Vernini [mailto:lucazeo@gmail.com] 
> Gesendet: Dienstag, 23. September 2014 11:59
> An: Weiss, Jörg
> Cc: pgsql-sql@postgresql.org
> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>
> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> > Hi!
> Hi.
>
> > Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
> > multiple columns of the reference table?
>
> Yes, it is.
>
> see here:
> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
> Section 5.3.5 there are some examples. One of them has multiple
> columns, just like your case.
>
> > Regards …
>
> Regards.

Thank you!

Do you mean this example?
CREATE TABLE t1 ( a integer PRIMARY KEY, b integer, c integer, FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
);
This is not, what I want.

In my case it should be something like this: 
CREATE TABLE t1 ( a integer PRIMARY KEY, b integer, c integer, FOREIGN KEY (b) REFERENCES other_table (c1,
c2='c2Value')
);
This example does not work. But I think you can see, what I mean.



Re: FOREIGN KEY Reference on multiple columns

From
Luca Vernini
Date:
Sorry, I don't get your problem.
In first example there was a where, in second case:
FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
You mean b must be equal to what?
Try to include real table script.
Probably you can use a check.

Regards,

Luca.

2014-09-23 13:38 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
>> -----Ursprüngliche Nachricht-----
>> Von: Luca Vernini [mailto:lucazeo@gmail.com]
>> Gesendet: Dienstag, 23. September 2014 11:59
>> An: Weiss, Jörg
>> Cc: pgsql-sql@postgresql.org
>> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>>
>> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
>> > Hi!
>> Hi.
>>
>> > Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
>> > multiple columns of the reference table?
>>
>> Yes, it is.
>>
>> see here:
>> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
>> Section 5.3.5 there are some examples. One of them has multiple
>> columns, just like your case.
>>
>> > Regards …
>>
>> Regards.
>
> Thank you!
>
> Do you mean this example?
> CREATE TABLE t1 (
>   a integer PRIMARY KEY,
>   b integer,
>   c integer,
>   FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
> );
> This is not, what I want.
>
> In my case it should be something like this:
> CREATE TABLE t1 (
>   a integer PRIMARY KEY,
>   b integer,
>   c integer,
>   FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> );
> This example does not work. But I think you can see, what I mean.
>
>
>
> --
> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql



Re: FOREIGN KEY Reference on multiple columns

From
Weiss, Jörg
Date:
I mean b must equal to c1  in the "other_table" where c2 has a certain value (for example c2 ). 

For my first example:
CREATE TABLE parm
( complex varchar(20) NOT NULL, para varchar(50) NOT NULL, sort int4 NOT NULL DEFAULT 10, value varchar(50)
NULL,CONSTRAINTparm_pkey PRIMARY KEY (complex, para, sort)
 
)

Table user 
CREATE TABLE user
( name varchar(20) NOT NULL, type integer NULL
)
In this case "type" of table user must equal to "value" of table "parm" and "para" must be "login_user" (for example)

Regards

Jörg

> -----Ursprüngliche Nachricht-----
> Von: Luca Vernini [mailto:lucazeo@gmail.com]
> Gesendet: Dienstag, 23. September 2014 14:37
> An: Weiss, Jörg
> Cc: pgsql-sql@postgresql.org
> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
> 
> Sorry, I don't get your problem.
> In first example there was a where, in second case:
> FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> You mean b must be equal to what?
> Try to include real table script.
> Probably you can use a check.
> 
> Regards,
> 
> Luca.
> 
> 2014-09-23 13:38 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> >> -----Ursprüngliche Nachricht-----
> >> Von: Luca Vernini [mailto:lucazeo@gmail.com]
> >> Gesendet: Dienstag, 23. September 2014 11:59
> >> An: Weiss, Jörg
> >> Cc: pgsql-sql@postgresql.org
> >> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
> >>
> >> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> >> > Hi!
> >> Hi.
> >>
> >> > Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
> >> > multiple columns of the reference table?
> >>
> >> Yes, it is.
> >>
> >> see here:
> >> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
> >> Section 5.3.5 there are some examples. One of them has multiple
> >> columns, just like your case.
> >>
> >> > Regards …
> >>
> >> Regards.
> >
> > Thank you!
> >
> > Do you mean this example?
> > CREATE TABLE t1 (
> >   a integer PRIMARY KEY,
> >   b integer,
> >   c integer,
> >   FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
> > );
> > This is not, what I want.
> >
> > In my case it should be something like this:
> > CREATE TABLE t1 (
> >   a integer PRIMARY KEY,
> >   b integer,
> >   c integer,
> >   FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> > );
> > This example does not work. But I think you can see, what I mean.
> >
> >
> >
> > --
> > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> > To make changes to your subscription:
> > http://www.postgresql.org/mailpref/pgsql-sql

Re: FOREIGN KEY Reference on multiple columns

From
Adrian Klaver
Date:
On 09/23/2014 04:38 AM, Weiss, Jörg wrote:
>> -----Ursprüngliche Nachricht-----
>> Von: Luca Vernini [mailto:lucazeo@gmail.com]
>> Gesendet: Dienstag, 23. September 2014 11:59
>> An: Weiss, Jörg
>> Cc: pgsql-sql@postgresql.org
>> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>>
>> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
>>> Hi!
>> Hi.
>>
>>> Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
>>> multiple columns of the reference table?
>>
>> Yes, it is.
>>
>> see here:
>> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
>> Section 5.3.5 there are some examples. One of them has multiple
>> columns, just like your case.
>>
>>> Regards …
>>
>> Regards.
>
> Thank you!
>
> Do you mean this example?
> CREATE TABLE t1 (
>    a integer PRIMARY KEY,
>    b integer,
>    c integer,
>    FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
> );
> This is not, what I want.
>
> In my case it should be something like this:
> CREATE TABLE t1 (
>    a integer PRIMARY KEY,
>    b integer,
>    c integer,
>    FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> );
> This example does not work. But I think you can see, what I mean.

Foreign keys do not support the when clause. In your original example 
there is also the problem that value is not part of a unique index or 
the primary key.

>
>
>


-- 
Adrian Klaver
adrian.klaver@aklaver.com



Re: FOREIGN KEY Reference on multiple columns

From
Luca Vernini
Date:
I see.
You cannot do a constraint with a "certain value", if I understood
right. This is not even possible in any know rdbms, because a
constraint must reference something stored on tables. Persisted on db.
You can only check values while inserting. I suggest useing a function.

Regards,

Luca.

2014-09-23 15:10 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> I mean b must equal to c1  in the "other_table" where c2 has a certain value (for example c2 ).
>
> For my first example:
> CREATE TABLE parm
> (
>   complex varchar(20) NOT NULL,
>   para varchar(50) NOT NULL,
>   sort int4 NOT NULL DEFAULT 10,
>   value varchar(50) NULL,
>  CONSTRAINT parm_pkey PRIMARY KEY (complex, para, sort)
> )
>
> Table user
> CREATE TABLE user
> (
>   name varchar(20) NOT NULL,
>   type integer NULL
> )
> In this case "type" of table user must equal to "value" of table "parm" and "para" must be "login_user" (for example)
>
> Regards
>
> Jörg
>
>> -----Ursprüngliche Nachricht-----
>> Von: Luca Vernini [mailto:lucazeo@gmail.com]
>> Gesendet: Dienstag, 23. September 2014 14:37
>> An: Weiss, Jörg
>> Cc: pgsql-sql@postgresql.org
>> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>>
>> Sorry, I don't get your problem.
>> In first example there was a where, in second case:
>> FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
>> You mean b must be equal to what?
>> Try to include real table script.
>> Probably you can use a check.
>>
>> Regards,
>>
>> Luca.
>>
>> 2014-09-23 13:38 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
>> >> -----Ursprüngliche Nachricht-----
>> >> Von: Luca Vernini [mailto:lucazeo@gmail.com]
>> >> Gesendet: Dienstag, 23. September 2014 11:59
>> >> An: Weiss, Jörg
>> >> Cc: pgsql-sql@postgresql.org
>> >> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>> >>
>> >> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
>> >> > Hi!
>> >> Hi.
>> >>
>> >> > Is it possible to create a “FOREIGN KEY CONSTRAINT” with references to
>> >> > multiple columns of the reference table?
>> >>
>> >> Yes, it is.
>> >>
>> >> see here:
>> >> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
>> >> Section 5.3.5 there are some examples. One of them has multiple
>> >> columns, just like your case.
>> >>
>> >> > Regards …
>> >>
>> >> Regards.
>> >
>> > Thank you!
>> >
>> > Do you mean this example?
>> > CREATE TABLE t1 (
>> >   a integer PRIMARY KEY,
>> >   b integer,
>> >   c integer,
>> >   FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
>> > );
>> > This is not, what I want.
>> >
>> > In my case it should be something like this:
>> > CREATE TABLE t1 (
>> >   a integer PRIMARY KEY,
>> >   b integer,
>> >   c integer,
>> >   FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
>> > );
>> > This example does not work. But I think you can see, what I mean.
>> >
>> >
>> >
>> > --
>> > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
>> > To make changes to your subscription:
>> > http://www.postgresql.org/mailpref/pgsql-sql
>
> --
> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql



Re: FOREIGN KEY Reference on multiple columns

From
Weiss, Jörg
Date:
That's what I wanted to know.
It's not only a constraint to a "certain value" or (better) "specific value", it should be a constraint to a
combinationof the values of 2 columns. 
 
"type" of table "user" must equal to "value" of table "parm" where "para" of table "parm"  must always be
"login_user".
Check or a function is not the same. A "foreign key" works on both sides. Table "user" and table "parm".
OK I can do checks at both tables ON UPDATE, INSERT or DELETE. This may work.  

Regards

Jörg

> -----Ursprüngliche Nachricht-----
> Von: Luca Vernini [mailto:lucazeo@gmail.com]
> Gesendet: Dienstag, 23. September 2014 15:18
> An: Weiss, Jörg
> Cc: pgsql-sql@postgresql.org
> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
> 
> I see.
> You cannot do a constraint with a "certain value", if I understood
> right. This is not even possible in any know rdbms, because a
> constraint must reference something stored on tables. Persisted on db.
> You can only check values while inserting. I suggest useing a function.
> 
> Regards,
> 
> Luca.
> 
> 2014-09-23 15:10 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> > I mean b must equal to c1  in the "other_table" where c2 has a certain value
> (for example c2 ).
> >
> > For my first example:
> > CREATE TABLE parm
> > (
> >   complex varchar(20) NOT NULL,
> >   para varchar(50) NOT NULL,
> >   sort int4 NOT NULL DEFAULT 10,
> >   value varchar(50) NULL,
> >  CONSTRAINT parm_pkey PRIMARY KEY (complex, para, sort)
> > )
> >
> > Table user
> > CREATE TABLE user
> > (
> >   name varchar(20) NOT NULL,
> >   type integer NULL
> > )
> > In this case "type" of table user must equal to "value" of table "parm" and
> "para" must be "login_user" (for example)
> >
> > Regards
> >
> > Jörg
> >
> >> -----Ursprüngliche Nachricht-----
> >> Von: Luca Vernini [mailto:lucazeo@gmail.com]
> >> Gesendet: Dienstag, 23. September 2014 14:37
> >> An: Weiss, Jörg
> >> Cc: pgsql-sql@postgresql.org
> >> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
> >>
> >> Sorry, I don't get your problem.
> >> In first example there was a where, in second case:
> >> FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> >> You mean b must be equal to what?
> >> Try to include real table script.
> >> Probably you can use a check.
> >>
> >> Regards,
> >>
> >> Luca.
> >>
> >> 2014-09-23 13:38 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> >> >> -----Ursprüngliche Nachricht-----
> >> >> Von: Luca Vernini [mailto:lucazeo@gmail.com]
> >> >> Gesendet: Dienstag, 23. September 2014 11:59
> >> >> An: Weiss, Jörg
> >> >> Cc: pgsql-sql@postgresql.org
> >> >> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
> >> >>
> >> >> 2014-09-23 11:54 GMT+02:00 Weiss, Jörg <J.Weiss@dvz-mv.de>:
> >> >> > Hi!
> >> >> Hi.
> >> >>
> >> >> > Is it possible to create a “FOREIGN KEY CONSTRAINT” with references
> to
> >> >> > multiple columns of the reference table?
> >> >>
> >> >> Yes, it is.
> >> >>
> >> >> see here:
> >> >> http://www.postgresql.org/docs/9.3/static/ddl-constraints.html
> >> >> Section 5.3.5 there are some examples. One of them has multiple
> >> >> columns, just like your case.
> >> >>
> >> >> > Regards …
> >> >>
> >> >> Regards.
> >> >
> >> > Thank you!
> >> >
> >> > Do you mean this example?
> >> > CREATE TABLE t1 (
> >> >   a integer PRIMARY KEY,
> >> >   b integer,
> >> >   c integer,
> >> >   FOREIGN KEY (b, c) REFERENCES other_table (c1, c2)
> >> > );
> >> > This is not, what I want.
> >> >
> >> > In my case it should be something like this:
> >> > CREATE TABLE t1 (
> >> >   a integer PRIMARY KEY,
> >> >   b integer,
> >> >   c integer,
> >> >   FOREIGN KEY (b) REFERENCES other_table (c1, c2='c2Value')
> >> > );
> >> > This example does not work. But I think you can see, what I mean.
> >> >
> >> >
> >> >
> >> > --
> >> > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> >> > To make changes to your subscription:
> >> > http://www.postgresql.org/mailpref/pgsql-sql
> >
> > --
> > Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> > To make changes to your subscription:
> > http://www.postgresql.org/mailpref/pgsql-sql

Re: FOREIGN KEY Reference on multiple columns

From
Tim Landscheidt
Date:
"Weiss, Jörg" <J.Weiss@dvz-mv.de> wrote:

> I mean b must equal to c1  in the "other_table" where c2 has a certain value (for example c2 ).

> For my first example:
> CREATE TABLE parm
> (
>   complex varchar(20) NOT NULL,
>   para varchar(50) NOT NULL,
>   sort int4 NOT NULL DEFAULT 10,
>   value varchar(50) NULL,
>  CONSTRAINT parm_pkey PRIMARY KEY (complex, para, sort)
> )

> Table user
> CREATE TABLE user
> (
>   name varchar(20) NOT NULL,
>   type integer NULL
> )
> In this case "type" of table user must equal to "value" of table "parm" and "para" must be "login_user" (for
example)

> [...]

You can achieve that by duplicating the para column to the
table user, adding a foreign key that matches both columns
to table parm and checks in table user whether para is
"login_user".  That doesn't work for NULLable columns,
though.

Tim




Re: FOREIGN KEY Reference on multiple columns

From
Weiss, Jörg
Date:

> -----Ursprüngliche Nachricht-----
> Von: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-
> owner@postgresql.org] Im Auftrag von Tim Landscheidt
> Gesendet: Mittwoch, 24. September 2014 20:03
> An: pgsql-sql@postgresql.org
> Betreff: Re: [SQL] FOREIGN KEY Reference on multiple columns
>
> "Weiss, Jörg" <J.Weiss@dvz-mv.de> wrote:
>
> > I mean b must equal to c1  in the "other_table" where c2 has a certain value
> (for example c2 ).
>
> > For my first example:
> > CREATE TABLE parm
> > (
> >   complex varchar(20) NOT NULL,
> >   para varchar(50) NOT NULL,
> >   sort int4 NOT NULL DEFAULT 10,
> >   value varchar(50) NULL,
> >  CONSTRAINT parm_pkey PRIMARY KEY (complex, para, sort)
> > )
>
> > Table user
> > CREATE TABLE user
> > (
> >   name varchar(20) NOT NULL,
> >   type integer NULL
> > )
> > In this case "type" of table user must equal to "value" of table "parm" and
> "para" must be "login_user" (for example)
>
> > [...]
>
> You can achieve that by duplicating the para column to the
> table user, adding a foreign key that matches both columns
> to table parm and checks in table user whether para is
> "login_user".  That doesn't work for NULLable columns,
> though.
>
> Tim
>
Yes of cause, this seems to be the best way.

Thank You!