Tell us what’s happening:
I can’t figure out what it is asking for in step 10
Blockquote STEP10: Each “star” should have a foreign key that references one of the rows in
galaxy
Your code so far
-- step1
CREATE DATABASE universe;
-- step2
\c universe;
CREATE TABLE galaxy();
CREATE TABLE star();
CREATE TABLE planet();
CREATE TABLE moon();
-- step3 & step4
ALTER TABLE galaxy ADD COLUMN id SERIAL NOT NULL;
ALTER TABLE galaxy ADD PRIMARY KEY(id);
ALTER TABLE star ADD COLUMN id SERIAL NOT NULL;
ALTER TABLE star ADD PRIMARY KEY(id);
ALTER TABLE planet ADD COLUMN id SERIAL NOT NULL;
ALTER TABLE planet ADD PRIMARY KEY(id);
ALTER TABLE moon ADD COLUMN id SERIAL NOT NULL;
ALTER TABLE moon ADD PRIMARY KEY(id);
-- step5
ALTER TABLE galaxy ADD COLUMN name VARCHAR(30);
ALTER TABLE star ADD COLUMN name VARCHAR(30);
ALTER TABLE planet ADD COLUMN name VARCHAR(30);
ALTER TABLE moon ADD COLUMN name VARCHAR(30);
-- step6
ALTER TABLE galaxy ADD COLUMN size INT;
ALTER TABLE star ADD COLUMN size INT;
-- step7
ALTER TABLE planet ADD COLUMN size NUMERIC;
-- step8
ALTER TABLE moon ADD COLUMN sec_name TEXT;
-- step9
ALTER TABLE galaxy ADD COLUMN wo BOOLEAN;
ALTER TABLE star ADD COLUMN wo BOOLEAN;
--step10
ALTER TABLE star ADD FOREIGN KEY(size) REFERENCES galaxy(size);
ERROR: there is no unique constraint matching given keys for referenced table "galaxy"
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