Re: FOREIGN KEY Reference on multiple columns

"Weiss, Jörg" <J(dot)Weiss(at)dvz-mv(dot)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