i got two tables with the following structures:
create table unit (
unit_id int4 not null primary key,
unit_name varchar(10) not null)
create table plant_unit (
pu_id int4 not null primary key,
unit_id int4 not null references unit (unit_id)
match all on delete restrict on update cascade)
that means the two tables are connected to each other
by the unit_id field. i cannot delete records from the
unit table if there is a relation in the plant_unit
table, and when i update the unit_id field in the unit
table the system will update all matching records in
the plant_unit table as well.
my question is how can i avoid to insert record into
the plant_unit table, when the specified unit_id is
not available in the unit table.
do i have to use trigger, or i miss something in the
constraint, or whatelse?
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