You have a wrong concept of foreign keys. "sta_type" is not a key of table
station_type, which cannot be referened as a foreign key.
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From: "Rich Shepard" <rshep...@appl-ecosys.com>
Sent: Friday, July 08, 2011 1:40 AM
To: <pgsql-general@postgresql.org>
Subject: [GENERAL] Add Foreign Keys To Table
I'm having difficulty finding the correct syntax to modify an existing
table. The modification is to add two columns, each a foreign reference to
the two key columns of another table.
The other table:
CREATE TABLE station_type (
sta_type VARCHAR(50),
secondary_type VARCHAR(50),
natural_indic BOOL,
PRIMARY KEY (sta_type, secondary_type)
);
When I try to alter the other table to add columns:
sta_type VARCHAR(50) REFERENCES station_type(sta_type) and
secondary_type VARCHAR(50) REFERENCES station_type(secondary_type)
I get syntax errors. For example,
alter table station_information add column sta_type varchar(50) references
station_type(sta_type);
ERROR: there is no unique constraint matching given keys for referenced
table "station_type"
alter table station_information add column sta_type varchar(50) not null
references station_type(sta_type);
ERROR: there is no unique constraint matching given keys for referenced
table "station_type"
alter table station_information add column sta_type varchar(50)
unique not null references station_type(sta_type);
NOTICE: ALTER TABLE / ADD UNIQUE will create implicit index
"station_information_sta_type_key" for table "station_information"
ERROR: there is no unique constraint matching given keys for referenced
table "station_type"
Reading the alter table document page for 9.x does not show me what I'm
doing incorrectly.
Rich
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